# CO2 and EI



## Christos Ioannou (18 Nov 2014)

Fact 1: CO2 is a super important in a planted tank.
Fact 2: EI fertilization method will provide more than adequate fertilization to your plants.

I assume that bubbles per second for CO2 is not a constant for all tanks: 3 bps will give less ppm of CO2 in a 50G tank than in a 10G tank.

Other than the monetary issue, seems to me that the only restricting factor for CO2 will be how much fish can handle.Is that a reasonable argument - the more CO2 the better? (without of course gassing fish/ shrimp)

Thank you.


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## Sacha (18 Nov 2014)

*popcorn*


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## Paulo Soares (18 Nov 2014)

Christos Ioannou said:


> the only restricting factor for CO2 will be how much fish can handle



Yes indeed... in my case i agree. I can´t puch to hard cause of the fish.


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## ian_m (18 Nov 2014)

Christos Ioannou said:


> I assume that bubbles per second for CO2 is not a constant for all tanks: 3 bps will give less ppm of CO2 in a 50G tank than in a 10G tank


Maybe, possibly. Depends on how well you dissolve your CO2 and how well you distribute it, might be easier and more successful in a larger tank.

When I first setup my tank, I used an in tank diffuser at 3-4 bps and got a slightly green drop checker. Moved to a inline diffuser and same tank at 1-2bps drop checker is yellow.

Use your bps to determine for your setup and your tank if you have gas flowing and is it high or low flow rate. Other than that you can't compare bps between different setups and tanks.


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## Marcel G (18 Nov 2014)

Let's say that your plants need 35 mg/L CO2 at most. Do you think that it's of any gain to add more?
What I want to say is that each organism has its limits of nutrient uptake. And I think that most plants in our tanks don't need too much CO2 to reach an unlimiting growth rate.


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## Christos Ioannou (18 Nov 2014)

ardjuna said:


> What I want to say is that each organism has its limits of nutrient uptake. And I think that most plants in our tanks don't need too much CO2 to reach an unlimiting growth rate.


Same stands for macro/ micro nutrients. EI sort of guarantees that these nutrients are readily available for plants.
Testing for a value of 35mg/L of CO2 could be an issue in its own right - so why not pump as much as possible? Does this ensure that CO2 is also readily available?


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## Marcel G (18 Nov 2014)

I assume that if you pump too much CO2 into your (critter-free) tank, then your pH could drop too much. If you have a pH aboud 6, then most of the nitrifying bacteria go dormant. At pH around 5 most of the bacteria (not only the nitrifying ones) are not working anymore. That's potential risk for planted tank. Also, if you reach some extreme level, then the high concentration begin to work against plants ... I mean, too much CO2 could prevent further growth and cause destruction (the same apply for other nutrients and light also).
_*It's always better to keep your parameters in some reasonable range.*_


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## Christos Ioannou (18 Nov 2014)

ardjuna said:


> I assume that if you pump too much CO2 into your (critter-free) tank, then your pH could drop too much. If you have a pH aboud 6, then most of the nitrifying bacteria go dormant. At pH around 5 most of the bacteria (not only the nitrifying ones) are not working anymore. That's potential risk for planted tank. Also, if you reach some extreme level, then the high concentration begin to work against plants ... I mean, too much CO2 could prevent further growth and cause destruction (the same apply for other nutrients and light also).
> It's always better to keep your parameters in some reasonable range.



This makes perfect sense now, thanks for your input!


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## Sacha (18 Nov 2014)

The Rubisco in the plants will re- adjust to whatever Co2 level is available. Basically, if you give the plants loads of Co2, they will get adjusted to this high level, so then if you need to reduce the Co2 level in the future, the plants will suffer because their uptake level will be affected. It will be a shock to their system that they are having to "search harder" to find the Co2.


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## parotet (18 Nov 2014)

Sacha said:


> The Rubisco in the plants will re- adjust to whatever Co2 level is available.


I'm pretty sure this 'whatever' has in practice a limit, due to side effects or limitation in uptake. 

Jordi


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## Sacha (18 Nov 2014)

Yes I'm sure it does. But remember that the vast majority of the "aquatic" plants we keep are not aquatic at all. In the wild, they grow exposed to the air, where Co2 levels are in the region of 400 ppm. So the Co2 level that they have adapted to is more than 10x that which we provide in our tanks.


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## pepedopolous (18 Nov 2014)

ardjuna said:


> If you have a pH aboud 6, then most of the nitrifying bacteria go dormant.



Ow! If what you're saying is true then my tanks are screwed! The pH is 7 before CO2 comes on and drops to around 5.8/5.9.

I've already artificially increased the KH from 0 to 4-5.

Cheers,

P


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## PARAGUAY (18 Nov 2014)

Recently started using EI in my 55gallon CO2 tank,to the rec. bottle dosage, plants going good but nitrate is getting very high, lightly stocked fish look ok. It recommends a weekly waterchange, I am thinking maybe more waterchanges, APF say the nitrate level not an issue but if I add new fish?Anybody?


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## ian_m (18 Nov 2014)

PARAGUAY said:


> but nitrate is getting very high,


What's the problem ? Due to a pump failure I ended up dosing nitrates at 400ppm with no issues. Where fish bothered ? Nope. Plants bothered ? Nope. Me bothered yes....that was 1 litre of EI solution wasted. Did 50% water change after it had been like this for a couple of days and just carried on EI dosing and weekly water changed.


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## PARAGUAY (18 Nov 2014)

The fish in the tank are a hardy lot(black widows,penguins,cardinals)and look ok.But the nitrate level a lot higher than when I used Tropica+, My main concern is adding new fish from another source so maybe do a 50% change just before adding.


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## ian_m (18 Nov 2014)

I assume you are not relying on a nitrate test kit to get your nitrate readings ?? If you are they will be hopelessly wrong, due to other substances in the water and you will be "wasting your worries" chasing something that isn't wrong....


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## PARAGUAY (18 Nov 2014)

Interesting that,but is that just nitrate testing results that are not so reliable, as the same results came when I checked with my local fs. I accept it may not be totally accurate but it is a indicator. The test kit used correctly gets a thumbs up from Nathan Hill PFK.


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## ian_m (18 Nov 2014)

PARAGUAY said:


> Iteresting that,but is that just nitrate testing results that are not so reliable


All of the results from hobby test kits. Remember shops just use slightly bigger boy hobby test kits and will get the same misleading results. The number of people that come here chasing a "non issue" as their test kits told them so...

No problem doing 50% water change before adding new fish, will certainly lower the organics and other waste in the water. But if your tap water is high in nitrate (50ppm max in UK) you will still have nitrate in the water. Are fish bothered, not really.


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## Sacha (18 Nov 2014)

PARAGUAY, please donate your test kit to your nearest charity shop. With the nights getting colder, hopefully somebody on the streets will be able to use it as good fuel for a fire.


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## the.tech.guy (20 Nov 2014)

Hi all, newby to the site here. OMG for give me.

Now I know this has probably been asked somewhere before on UKAPS but as I'm new to the site I just can not find it.

I have just added a pressurised CO2 system to my tank for the first time and am running it at 2 BPS but the Drop checker will not go green ( I'm scared I will kill the fish if i get this wrong). I am using Ei dozing for the plant fertiliser which is all so new to me.

The question I have is will a PH automatic controller he any good?

Any help with this will be most appreciated even if it's to point me to the right part of the site.

(Tank is 48" by 15" by 18" tall but it's not fill all the way to the top so it's about 177 litres of water ) heavily planted.

(Ei Dozing is the start set from Aquarium Plant Food UK, KN03,KH2PO4,MGS04 + Chelated Trace) 

(Co2 is from co2 supermarket the sodaStream set up)

HELP HELP HELP


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## Martin in Holland (21 Nov 2014)

I found that getting the CO2 right is the most difficult part in our hobby, because CO2 is not just pump it into your tank and voila....it also has to do with flow/ distribution, plant mass and more. I pumped in as much CO2 as the fish could handle and went little by little down until the plants started to show signs that they needed more...upped a bit and now I'm fine (I think  )


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## Christos Ioannou (21 Nov 2014)

the.tech.guy said:


> I have just added a pressurised CO2 system to my tank for the first time and am running it at 2 BPS but the Drop checker will not go green ( I'm scared I will kill the fish if i get this wrong). I am using Ei dozing for the plant fertiliser which is all so new to me.


For what's it is worth, the BPS in my bubble counter are beyond counting, on a tank of similar size (55" x 15" x 13"), to achieve a pH drop of 1 unit before lights come on. (co2 is on 2hrs before lights come on, and goes off 1 hr before lights go off) as far as a ph automatic controller is concerned, I suppose that this may result in fluctuating co2, which will bring algae in your setup. I am also using an inline co2 atomizer and a powerhead for better circulation. Fish, shrimp seem to be just fine.

From a fellow newbie, good luck.


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## the.tech.guy (21 Nov 2014)

Thanks all for your in put, I was thinking that same about the PH Controller so i think i will give it a miss for now.


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## ian_m (21 Nov 2014)

the.tech.guy said:


> am running it at 2 BPS but the Drop checker will not go green


I would suggest you have a leak somewhere. I have less than 2bps with JBL bubble counter and in my 180l tank drop checker is like this anywhere in the tank.





Before I located all the leaks in my CO2 system I had quite high bubble rate and drop checker barely moving off blue. Dunk all the CO2 (except FE of course) in to a bucket of water and wiggle the tubes and find all your leaks. I am using an inline diffuser on filter outlet.


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## X3NiTH (21 Nov 2014)

The other way to use a controller to regulate the co2 in a tank is to control how the gas escapes the tank. You can use this UP pH controller from co2Art to control an air supply to off gas co2 rather than close the solenoid on the co2 and have the system depressurise. I have a Weipro controller also, if this is used to control the co2 solenoid there will be a fluctuation of 0.2pH around the desired set point. Using the UP in LO mode to control off-gassing rates via an Airstone there is a fluctuation of 0.1pH, the crucial difference is the co2 never gets switched off and continues to come into the tank at the same injection rate. Blowing the extra gas off is quicker than depressurising the system and waiting for the gas to leave the tank naturally. 

You still have to Nanny a controller because they don't learn the pH fluctuation in the tank due to biological influences or EI dosing. It's a good way to prevent untimely fish deaths (providing you have it all configured right) due to too much co2.


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## plantbrain (21 Nov 2014)

ardjuna said:


> I assume that if you pump too much CO2 into your (critter-free) tank, then your pH could drop too much. If you have a pH aboud 6, then most of the nitrifying bacteria go dormant. At pH around 5 most of the bacteria (not only the nitrifying ones) are not working anymore. That's potential risk for planted tank. Also, if you reach some extreme level, then the high concentration begin to work against plants ... I mean, too much CO2 could prevent further growth and cause destruction (the same apply for other nutrients and light also).
> _*It's always better to keep your parameters in some reasonable range.*_




pH drop has nothing to do with it, respiration of heterotrophes do. Bacteria, inverts, fish etc. 
If you have a high ppm of CO2 and the O2 stays the same, then it'll be harder and harder to respire. 
I'd assume that it also the care for plants since they respire also, but after say 50-70 ppm of CO2, there's not much point. 

You gain nothing by adding more than that, 35 ppm is not the overall limit.
35 ppm MIGHT be for a tank full of Anubias with say 40 umol of light.
But likely will not be with a tank full of touchy stem plants with 120umols of light.

Likewise, adding full EI to a tank with sediment ferts, low light, slower growing plants, might be larding it on................while another high light stem tank might perfect. 
EI is just a non limiting start point. 

You can treat CO2 the SAME way, but CO2 is much more toxic than the ferts.
And people mess it up more than fertilizers.

Light is pretty stable.
So adjusting the light, not the ferts, often helps a lot if you have trouble with CO2.

Still, CO2 management is the biggest problem for new and even old planted hobbyists.


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## Marcel G (22 Nov 2014)

plantbrain said:


> 35 ppm is not the overall limit.
> 35 ppm MIGHT be for a tank full of Anubias with say 40 umol of light.
> But likely will not be with a tank full of touchy stem plants with 120umols of light.


I have a tank right now where I have 100-120 µmol PAR at the substrate, and about 400 µmol PAR at the water surface. And my CO2 concentration (according to the dropchecker) is somewhere around 15-20 mg/L CO2. The O2 level in my tank is somewhere around 80 and 115% of O2 saturation level (see picture) → 80% at night, and 110-115% during photoperiod.




Here's a picture of this tank:




Do I have any algae problems? No.
Do I need to use EI in there? No.
Do I have any nutrient deficiencies? No.
Do I need more then 20 mg/L CO2 to have a nice algae-free high-light planted tank? No.
Do I need to bother with CO2 management (the same way EI users do)? No.


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## Martin in Holland (22 Nov 2014)

S


ardjuna said:


> I have a tank right now where I have 100-120 µmol PAR at the substrate, and about 400 µmol PAR at the water surface. And my CO2 concentration (according to the dropchecker) is somewhere around 15-20 mg/L CO2. The O2 level in my tank is somewhere around 80 and 115% of O2 saturation level (see picture) → 80% at night, and 110-115% during photoperiod.
> 
> 
> 
> ...



So you are saying that when using EI my CO2 will be more in demand?


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## Marcel G (22 Nov 2014)

No, I'm saying that 15-20 mg/L CO2 may be sufficient for a good growth of even the most demanding plants under very strong light. There's absolutely no point IMO to head for 50-70 mg/L. I'm not a plant seller, so I don't need to have a tons of biomass each week in my tank. If you use EI and lot of CO2, then your plants will grow like crazy, and you'll enter into the realms of big problems with good CO2 management (as one of my friend noted). Any mistake with CO2, and you end up with a lot of algae and bad plant growth. So with EI you got rid of nutrient deficiency problems, but immediately you end up with much worse problems of good CO2 management (which is according to Tom Barr the most tricky thing to set correctly).

I keep lower CO2 levels, and lower nutrient levels, and even under strong light I have no problems with algae or bad plant growth. And if I want some growth boost, then I increase PO4 dosage a little, and in just one week all my stem plants are reaching the water surface (with the same CO2 level of 15-20 mg/L under 100 µmol PAR at the substrate). I really see no point in pumping tons of nutrients, and tons of CO2 in there, to produce tons of biomass each week ... and to get into serious troubles with good CO2 management.


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## parotet (22 Nov 2014)

Absolutely agree with this. I'm not sure 100% which is the physiological mechanism behind all this but in my mid light (70-80 micromol PAR) tank with good co2, see my ph drop below, dropchecker yellowish, etc. I never get rid of BBA in the old leaves or difficult areas of the tank (to the eyes of everyone it is a free algae tank, but not for a planted tank hobbyist)

http://www.ukaps.org/forum/threads/new-setup-from-2-to-just-plants.34374/page-2

IMO, EI recommended levels for PO4 (at least the ones in this site or Barr's site) boosts plants' growth very significantly, and once this nutrient is not limited anymore, CO2 is again the most limiting or at least the most difficult parameter to meet... Probably to high biomass to be fed? To more difficult flow due to the biomass growth? not really sure, but it seems that good CO2 is more difficult to achieve and BBA appear.

I have noticed significant changes just using an EI method with lower PO4... Let's say adding 1 ppm instead of 3-5 ppm of PO4. My previous light and my previous CO2 (according to ph drop should be around 30-40 ppm) is now perfect and the tank looks nearly algae free.

Ok, once we are here (nothing new for most of you I'm sure), the answers would be:

- 'that is because you have too much light'. And my reply would be that reducing light is the key points of course, but not only for EI but for all the planted tanks methods. The fact is that now my light is the same and co2 demand is more feasible

- 'EI never said to use fix values, just decrease the amounts use until you notice side effects'... Ok, so we are not in that method of unlimited amounts, we are getting close to other approaches, such as PPS-Pro. Anyway, I don't care which name or brand the method has, but if we have to decrease to adjust the system, IMO the method lose part of its point

- 'you need more co2'. I think I am not a newbie on this. I've been fine tuning my setup for two years, my estimations of CO2 (I don't own a co2 meter) all seem to point in the right direction. It also amazes me how high co2 has to be in most of the high light EI tanks... Because CO2 is by far the most difficult issue in a planted tank. So a method that was intended to be for the newbie (no test, no accuracy in dosing...) ends up with super demanding co2 levels (agree that mostly when playing with high light)

- 'you blame PO4 and it is demonstrated that PO4 is not responsible for Algae'. And I totally agree. It is not PO4 to be blamed, umy guess is that PO4 high levels drives to very demanding CO2 levels which are very difficult to achieve. Therefore PO4 do not create algae but creates an scenario in which BBA can easily appear.

Of course I may be wrong in some of the assumptions I made and I would be very happy if someone can point out why I am wrong.

Jordi


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## pepedopolous (22 Nov 2014)

OK Parotet,

Can you quantify your mix of PO4 in teaspoons? I used 4 teaspoons of KNO3 and 1 teaspoon of KH2PO4 in 500ml of water. Then when I got some problems with GSA/GDA on my _Staurogyne_ I increased the KH2PO4 to 2 teaspoons and I haven't stopped using this mix even though the GSA/GDA has gone.

However, BBA is always coming back regardless of flow, CO2 or light.

Thanks,

P


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## Martin in Holland (22 Nov 2014)

Maybe Tom Barr can elaborate on this, after all he is the EI guy.


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## parotet (22 Nov 2014)

pepedopolous said:


> OK Parotet,
> Can you quantify your mix of PO4 in teaspoons? I used 4 teaspoons of KNO3 and 1 teaspoon of KH2PO4 in 500ml of water. Then when I got some problems with GSA/GDA on my Staurogyne I increased the KH2PO4 to 2 teaspoons and I haven't stopped using this mix even though the GSA/GDA has gone.
> However, BBA is always coming back regardless of flow, CO2 or light.
> Thanks,
> P


Hi, someone did this work in UKAPS some long ago...
http://www.ukaps.org/forum/threads/teaspoons-to-grams-conversion-via-chemical-density.33331/

4 tsp of KNO3 = 42 g
2 tsp of KH2PO4 = 23.4 g

Using any of the available nutrient calculators and introducing the volume of your tank and you will see what are you dosing to the water column... but it seems quite a lot of KH2PO4 to me. Anyway, I'd give the floor to someone else with more experience and knowledge so we can have good and reliable advice on my "probably not that good theory about high PO4 driving to more demanding CO2 and more chances of BBA".



pepedopolous said:


> I increased the KH2PO4 to 2 teaspoons and I haven't stopped using this mix even though the GSA/GDA has gone.



As mentioned by Marcel (aka ardjuna) in another thread about nutrients' plant consumption, dosing high levels of nitrates and phosphates (I mean not just an excess but a large excess) can have cross-cutting benefits beyond plants' nutrition, which is fighting against blue diatoms or GSA (these algae don't like high levels of these nutrients... have you ever had blue Green diatoms... just sprinkle some nitrates over and gone). Or as suggested in this thread, maybe very high CO2 levels can also help to prevent algae... when I reduced the PO4 EI standard dose (3-5 ppm, closer to 5 ppm; then went to 1-2 ppm) in my tank I did it very slowly to be aware of the effects and... yes these algae appeared but nothing to be worried about.

Jordi


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## Marcel G (23 Nov 2014)

_*Weekly nutrient consumption*_ according to my two tests (I do other tests also to verify these data, but they are not finished yet):
Tank #1: 62L → 3 g CO2, 3 mg/L NO3, 0.2 mg/L PO4, 0.6 mg/L K, 0.001 mg/L Fe → 100-120 µmol PAR at the substrate
Tank #2: 112L → 6 g CO2, 4 mg/L NO3, 0.2 mg/L PO4, 0.7 mg/L K, 0.001 mg/L Fe → 70-100 µmol PAR at the substrate
Both tanks are high-tech ones. By raw estimate I add to the first tank around 4.7 g CO2 per day (just during the photoperiod), which is ~33 g CO2 per week. At that time my dropchecker was lime-green (~35 mg/L CO2). In the first tank I fertilized sporadically (still I did not saw any nutrient deficiencies in there). In the second tank the fertilizing regime was as follows: 7 mg/L NO3, 6 mg/L K, 0.8 mg/L PO4, 0.8 mg/L Fe (weekly).

From the above results of my tests I would say that CO2 is somewhere close to the saturation point in most tanks. So when we maintain 35 mg/L CO2, we may have 10-times more than our plants really need (in most setups). So even if we would have ~10-15 mg/L CO2, still this should give us nearly the same results (in "normal" densely planted high-light tanks with a strong light of 100 µmol PAR at the bottom). Also, I think that most of us add much more than 3 mg/L NO3, 0.6 mg/L K, 0.2 mg/L PO4, and 0.001 mg/L Fe into our tanks. In the second test we added 0.8 mg/L PO4 weekly, so if you add 3 mg/L PO4 each week, then your plants will probably grow even more ... but the percentage difference should not be high. But do we really want our plants to grow like crazy? Is there anyone (except the ones who sell plants) who wants his plants to grow like crazy? Is there anyone who revels in trimming his plants each week?

In water, the uptake of CO2 is limited by slow diffusion. Although we can raise CO2 concentration in our tank, our aquatic plants are still limited by slow gaseous diffusion. High CO2 levels in the planted aquarium allow the plants to use less nitrogen for Rubisco. So, if less enzyme is needed because the CO2 concentration is high, the proteins can be used in other processes in the plants leading to formation of new biomass. So at higher CO2 level, less nutrients are needed.

According to the study of Andersen & Pedersen, at 250 µmol PAR and 7 mg/L CO2 the growth rate (= increase of plant biomass) is approx. the same as at 90 µmol PAR and 40 mg/L CO2. Also the difference between 250 µmol PAR and 40 mg/L vs. 250 µmol PAR and 7 mg/L (or vs. 90 µmol PAR and 40 mg/L) is only 40% in plant biomass. So if we have a strong light (250 µmol PAR), and then we raise our CO2 concentration from 7 mg/L to 40 mg/L, we gain only 40% of plant biomass (i.e. our plants will grow only by 40% more).


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## pepedopolous (23 Nov 2014)

Hi guys,

EI can mean NO3 concentrations of anything from 5-30ppm and PO4 concentrations of 1.0 to 3.0ppm.

According to the nutrient calculators, the EI recipe I use (from aquariumplantfood.co.uk) gives 5.10ppm NO3 and 1.56ppm PO4.

With such a wide range of concentrations for NO3 in particular, can I be sure that I have 'unlimited' NO3? 

Also what on earth do people mean when they say they dose 2*EI? This could be anything from 10 to 60ppm NO3 I suppose, but 10-30ppm is in the range of normal EI!

P


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## Martin in Holland (23 Nov 2014)

ardjuna said:


> _*Weekly nutrient consumption*_ according to my two tests (I do other tests also to verify these data, but they are not finished yet):
> Tank #1: 62L → 3 g CO2, 3 mg/L NO3, 0.2 mg/L PO4, 0.6 mg/L K, 0.001 mg/L Fe → 100-120 µmol PAR at the substrate
> Tank #2: 112L → 6 g CO2, 4 mg/L NO3, 0.2 mg/L PO4, 0.7 mg/L K, 0.001 mg/L Fe → 70-100 µmol PAR at the substrate
> Both tanks are high-tech ones. By raw estimate I add to the first tank around 4.7 g CO2 per day (just during the photoperiod), which is ~33 g CO2 per week. At that time my dropchecker was lime-green (~35 mg/L CO2). In the first tank I fertilized sporadically (still I did not saw any nutrient deficiencies in there). In the second tank the fertilizing regime was as follows: 7 mg/L NO3, 6 mg/L K, 0.8 mg/L PO4, 0.8 mg/L Fe (weekly).
> ...



Shouldn't you also mention which kind of substrate you are using in those tests? ADA amazonia for instance is high in nutrients, as are many more or maybe you even added some tabs to your substrate....and so on ....
Anyway, I just did a 4 day black out in my BBA invested 40 liter tank which I used the EI method and will now try to use Tetra Flora Pride (3ml every other week) inject CO2 with pressure bottle, the substrate is a small grain gravel only without any nutrients added.


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## Marcel G (23 Nov 2014)

The values I stated above are not what I added to the tanks (actually I added much more than that), but what plants used up.


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## Marcel G (23 Nov 2014)

Look at this article: "Comparison of the photosynthetic characteristics of three submersed aquatic plants". This article is a key to understanding how much CO2 aquatic plants are able to use up. Let me summarize it a little:
The study discusses three aquatic plants (weeds) and their photosynthetic rates at non-limiting light and CO2 levels.
According to this study these aquatic plants have the following _*half saturation levels of CO2*_ (Km):
1) Hydrilla verticillata: 170 µM = _*7.48 ppm*_ (at pH 4), 90 µM = 3.96 ppm (at pH 8)
2) Myriophyllum spicatum: 150 µM = _*6.60 ppm*_ (at pH 4), 75 µM = 3.30 ppm (at pH 8)
3) Ceratophyllum demersum: 165 µM = _*7.26 ppm*_ (at pH 4), 95 µM = 4.18 ppm (at pH 8)
The 100% _*saturation level of CO2*_ is 0.5 mM = _*22 ppm*_ (0.5 * 44 g/mol).
These values applies for a temperature of 30°C, and light intensity of 1000 µmol PAR !!!
The authors say, that the above half saturation levels of CO2 (Km) _"probably represent close to the maximum rates attainable by these three species at 30 C, and as far as can be ascertained, they are the highest rates reported for submersed aquatic flowering plants"_.

So, what does it mean? "Half saturation level" of CO2 means such a conditions where plants have 50% of the maximum CO2 which they are able to use up under ideal conditions. If you add more then this, your plants will actually grow more, but not that much. I would say that at this half saturation level of CO2, plants reach about 70-80% _(authors say "close to the maximum rates")_ of the maximum growth rate. So these plants can grow at ~70% of their potencial with as low CO2 concentration as 4-7 ppm! And the maximum level they are able to utilize is 22 ppm CO2.

Beware: These are extremes (at 30°C, 1000 µmol PAR, and with aquatic weeds), and not averages (25°C, 100 µmol PAR, and variety of different low- and high-light aquatic plants) !!!

So again my question: Is there any need or reason for us to aim for more then _*10-20 ppm of CO2*_ to have a good growth?

The paradox is that even T.Barr in his main EI article on Barr Report says that:
_"The maximum CO2 level no matter what light set up you might have is about 30ppm* for these three very fast growing weeds, which we can assume have higher CO2 needs/demand than slower growing aquarium plants subjected to less intense lighting than sunlight."_
*He made a mistake in converting mM to ppm (it should be 22 ppm).


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## Marcel G (23 Nov 2014)

pepedopolous said:


> EI can mean NO3 concentrations of anything from 5-30ppm and PO4 concentrations of 1.0 to 3.0ppm ... With such a wide range of concentrations for NO3 in particular, can I be sure that I have 'unlimited' NO3? ... Also what on earth do people mean when they say they dose 2*EI? This could be anything from 10 to 60ppm NO3 I suppose, but 10-30ppm is in the range of normal EI!


This question should be answered by the author of EI method (Tom Barr) in the first place. But if he says that some (unspecified) plants can consume up to 30 ppm of NO3 per week*, and you (of course) don't know if it's your case (i.e. if you have these plants in your tank), then I suppose you should aim for the higher end of the range ... to be safe. That's (I think) the reason why people say that EI means 30 ppm NO3, 3 ppm PO4 ... etc. So when some people say they use 2xEI, it means that they are just extremists who have no idea of what can mean "unlimiting". 

*PS: Have a look at post #27, where there is a picture of my densely planted tank with unlimiting CO2 levels (~20 mg/L) and strong light (100 µmol PAR at the bottom) with a weekly consumption rate of about 3 ppm of NO3.


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## parotet (23 Nov 2014)

Marcel, I wonder if such high injection levels we have in our tanks are needed to meet these uptake quantities mentioned in your post. Maybe we need to inject twice or three times the plants can uptake because our diffusion efficiency is low (i.e. We need to ripple the surface in order to reach stable levels and we know this degasses the water column)

Jordi

Edit: good distribution of co2 in all the tank can be another good reason to add much more gas than the plants need?


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## Marcel G (23 Nov 2014)

I think this is not true in the case of CO2. The authors of the above study say that saturation point of free CO2 was 0.5 mM (= 500 µM), which is 22 ppm ... and the half saturation point 150-170 µM, which is 6.6 to 7.5 ppm. This is the concentration measured in the water, rather then an amount the plants actually used up. So if we want to have an unlimiting CO2 level in our tanks, we need no more then 20 ppm (actually much less as we don't have 1000 µmol PAR nor 30°C most of the time, and we don't have tanks where 100% of plants are weeds). If our dropchecker says we have 20 ppm we may "rest in peace" (and even with 10 ppm all our plants should do just fine) as it means that this amount of CO2 is already dissolved in the water ... so there's no need to worry much about good distribution ... as long as we have some flow, the CO2 should get to all our plants. So as I already mentioned, the uptake of CO2 is limited by slow gaseous diffusion; even if we raise CO2 concentration in our tank (to more then 20 ppm), our aquatic plants will be still limited by the slow gaseous diffusion. So as I understand it, when plants have 20 ppm of CO2 dissolved in the water, the rate of gaseous diffusion reaches its maximum potencial. And again: This applies to fast growing weeds under extremely strong light and high temperature! In normal (average) conditions of our planted tanks, we never ever meet such a conditions.

On the other hand, high (= totally unnecessary and highly unlimiting) levels of some nutrients (e.g. PO4 or CO2) may have negative effects on some kinds of algae. So if I have a high level of nutrients in my high-tech tank, under normal conditions I would suffer from algae (after couple of weeks, and without regular maintenance and some algivores). But if I raise the nutrient concentrations to some extreme levels, it may suppress algae. But it's a mistake (IMO) to make some general conclusions that high level of nutrients pose no risk for me in regard to algae (but that's another story).

So in my opinion, the people who are driving their nutrient levels to extremes (50-70 ppm CO2, 30-60 ppm NO3, 3-10 ppm PO4, 1-2 ppm Fe) are not good horticulturalists but good algae killers. They are making a dangerous and poisoning environment for algae ... that's all. If you get too much light, it will burn you. If you add too much nutrients into your tank, it will create an environment hostile to lower life (like algae). That's my hypothesis.


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## plantbrain (23 Nov 2014)

ardjuna said:


> I have a tank right now where I have 100-120 µmol PAR at the substrate, and about 400 µmol PAR at the water surface. And my CO2 concentration (according to the dropchecker) is somewhere around 15-20 mg/L CO2. The O2 level in my tank is somewhere around 80 and 115% of O2 saturation level (see picture) → 80% at night, and 110-115% during photoperiod.
> 
> 
> 
> ...



There are some other factors that appear overlooked:

Temperature

Also, while you provide good O2 data(more about that later) Drop checkers are woefully POOR methods to measure CO2.
Relative pH might be better, but the tank you have does not degas particularly well and you need to keep the water for evaporation loss topped off. 
But nano tanks tend to degas(as well as pull in O2 from the air) better than larger tanks with canisters. The only concern is the drop in O2 at night, it's considerably less than mine, but for a nano tank, getting a wet/dry or a surface skimmer etc, it's a poor trade off. 

However, the 100% DO level @ almost 9 ppm suggest that your aquarium is pretty cool, as in ~20C.
If the tank is say 30C, then more in the 100% range would be around 7 ppm for O2.

Question: will the growth be slower and the demand for CO2/nutrients be LESS or MORE as the temp increases?
MORE.

So you can get away with LESS CO2 at lower temps. Even with higher light etc.
DEMAND is LESS, for CO2 and nutrients both, you have nutrients, you have sediment that appears to be clay based like ADA AS etc. 
I do not see any fish. I also do not know the water change frequency nor the tap water, in the UK, a lot of tap has ample NO3......GH and other nutrients. 

Temps are a factor often NOT discussed or considered but can play a large role.

As true for all gases dissolved in water, as the temp increases, so the % in the water is reduced.
Fish metabolism also slows down, so they have less demand for O2 while having more available.

I agree, there's no need or good reason to dose @ 2x EI.

I would spend more time measuring and looking at CO2, less at O2. 
Wiser to keep the tank cooler.

But if you live in a tropical area, or where it gets very warm and you lack air conditioning or you keep discus and cardinals, other warmer water fish species..................like many is Asia, then you are left with little choice.
But smaller tanks and shrimp? then it's great. Which is what most shrimp folks do, no CO2, lower light plants, cooler temps around 18-20C.  

Not surprising and gives a good illustration how the Q10 biology idea works with temps. 
If you added temps to 10C higher, then the demand would be 2x that same CO2 rate. 

Try it and see.

Ferts/light and CO2 are not the only limiting factors to growth, temp is one as well.


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## plantbrain (23 Nov 2014)

ardjuna said:


> Look at this article: "Comparison of the photosynthetic characteristics of three submersed aquatic plants". This article is a key to understanding how much CO2 aquatic plants are able to use up. Let me summarize it a little:
> The study discusses three aquatic plants (weeds) and their photosynthetic rates at non-limiting light and CO2 levels.
> According to this study these aquatic plants have the following _*half saturation levels of CO2*_ (Km):
> 1) Hydrilla verticillata: 170 µM = _*7.48 ppm*_ (at pH 4), 90 µM = 3.96 ppm (at pH 8)
> ...




Those 3 species are fast growing weeds. They have better ability to compete than most every species we keep in aquariums. 
  They can start photosynthesis at a lower light and meet respiration demands(thus actually "grow" have a net gain of fixed carbon).
However, do you think ALL 400+ species and types that are kept in aquariums have the same ability to fix carbon?

If we all kept say Hydrilla, then no one would use CO2. 

You can make some assumptions from the paper: things like:
1. Plants will have a similar light/CO2 curve and it's not linear
2. Temperature will impact these rates
3. Different species will compete differently at the same light and CO2 concentrations(A big reason why we add CO2 other than increasing the rates of growth)
4. From 3, you might assume that most of the other plants will have MORE CO2 demand than say Hydrilla. 
5. Plants still grow with LESS than non limiting CO2, they grow without ANY added CO2, they just grow slower.
6. 30C was chose because that's a common summer time temp in Florida waters/lakes where the study was done. So you could assume the temps will be less. That's a fair assumption you made. At least for Hydrilla, milfoil and Cabomba(all noxious weeds present near me also). 
7. Under cooler conditions, the plants listed will have LESS CO2 demand. Other species might compete better being better adapted at cooler temps also.

Ultimately, there'a a wide range of ppm for CO2 that is good for the very wide range of types of planted tanks.
There's no way my tank here at 26C would do well with 15-20 ppm of CO2. 



It needs ~55 ppm.
I do not target that amount, I watch the plants and algae. THEN, I go back and try to measure and use a few tricks to get a good ppm measure. 
My warmer tank, the 180 Gallon? 30 C? It needs around 60-70 ppm.
The Buce tank seems decent at 40-45 ppm.

I do not blindly apply theory.
I apply good observations and then go back and measure. 
EI was done that way, then I went back and made some assumptions. 

Over time, I can see if something goes wrong...........say the CO2 is off, or some other issue. Then I know what the plants and algae are doing, fish activity etc. 
Becomes easy to spot. When you have slow changes over time like temp in the home, or water chemistry KH changes......then it can catch many of us off guard.
Or a poor measurement. 

Generally, we over look something or make a bad assumption that gets us in trouble. 
We all do it, Amano to the newbie.


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## plantbrain (23 Nov 2014)

ardjuna said:


> So in my opinion, the people who are driving their nutrient levels to extremes (50-70 ppm CO2, 30-60 ppm NO3, 3-10 ppm PO4, 1-2 ppm Fe) are not good horticulturalists but good algae killers. They are making a dangerous and poisoning environment for algae ... that's all. If you get too much light, it will burn you. If you add too much nutrients into your tank, it will create an environment hostile to lower life (like algae). That's my hypothesis.



You assume that it is a dangerous environment, but is it? Where is the evidence?
People have claimed this for decades, yet when tested under controlled conditions, there's no risk observed.
You need to have good observations, that support the claim under controlled conditions.
If you have algae, then the conditions are not controlled obviously.

So the only risk is not the method, rather, the user's ability to do the method.
In otherwords, it's people, not the method that is to blame.
The method does work well and there's no doubt of that.

That said, I agree with you that there's no NEED to lard it on, I've never argued that should be done. 
30ppm is a good starting point if you want a ppm for CO2, then adjust from there slowly and progressively. 
10-20 ppm seems a decent residual for NO3 
PO4, seen all sorts of ppm's, but I dose 5 ppm 2x a week.
Fe, whatever looks best, but my ppm's are in the 1-2 ppm ranges also for the stem tanks and even the Buce tank, I dose the same amount with obviously good effects. I have sold 4000$ worth of plants from that tank this year. 
That tank is the coolest, running about 22 C and about 25C in the summer. Ariods seem to like more traces than other plant families. Bob Gasser(Crypt grower) taught me that via experience.

My focus is and always has been on the plants, not the algae. That has remained unchanged. 
I have tried to induce algae. This is to see if there's any support for algae claims. 

Good horticulture is focused on pest management as well care, and good growth, not just some fert routine. 
Shrimp, temps, good trimming methods and post trimming care, water changes, plant choices etc.
Plenty of other issues ...we humans.............overlook.

All methods "work", but the people are much more the issue. 
Still, depending on your goal, different management can be done to best suit that goal.

So figure out their goal 1st, then.............find a good management method to meet that goal.
I do not blindly suggest EI, I never have.

I suggest non CO2, Excel, lower light, cooler temps, easier plant species, better plant choices, better trimming routines, better water change routines etc etc


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## GHNelson (23 Nov 2014)

Horses for courses springs to mind!
Every tank is unique..95% will have some sort of algae issue be it small or large.
Even in the most perfect looking aquarium there maybe algae trying to get a foothold...Tom knows this and that comes with experience.
Its dealing with it in the correct manner to eradicate it and to prevent further issues down the line, that is the key! 
hoggie


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## pepedopolous (23 Nov 2014)

Hi guys,

My plants are unhealthy, dosing '2xEI' is said to be unnecessary. 

However, my EI mix, following the manufacturers recipe, provides only 5.1 ppm NO3. 

Now I've maxed-out CO2 to the best of my ability, should I increase NO3 to 30 ppm?

Totally confused!

P


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## Marcel G (23 Nov 2014)

Tom, let me comment your statements, and ask you a few questions:
1) As to the temperature. I can present the same chart for temp. Actually I work on an article concerning nutrient consumption right now, so I'll present all data there (but it will take a couple of months). Temp is just one factor out of many which can play a role in photosynthesis rate. So yes, in the test tank #1 the temperature was quite low (20.5 to 21°C). But I did the same test in another tank where the mean temperature was about 26 to 26.5°C. The results were actually similar. That being said, I believe that at higher temperature there may be some increase in growth.
2) As to the CO2 saturation, maybe I got it wrong from the paper, but if you would measure carbon content in dry mass, then you would find out that the plants are just not able to utilize all the CO2 we supply them. In my practical tests the plants were able to utilize maybe 1/10th of the amount I was supplying them. Also there's a huge number of tanks where the CO2 is distributed using a simple diffuser, and the concentrations are kept quite low. Still the plants do very well.
3) If you say that your tank at 26°C won't do well with 15-20 ppm of CO2, and that it needs 55 ppm ... what exactly happens if you supply 15-20 ppm? Do you get algae, or do the plants die? I have quite a lot of experiences with 15-20 ppm of CO2 in my tank with good algae-free growth under high light (70-100 µmol PAR and temps in the range of 20-27°C). So I would like to know what risk may such a low CO2 level pose?
4) You say that you do not blindly apply theory, but rather good observations. Does it mean that if someone else cites some scientific papers to support his claims, that his claims have less weight? This type of argument is quite widespread, and often used in different forums.
5) It seems you misinterpreted my statement about dangerous environment. I said that you probably create a dangerous environment for algae (not plants or critters). And is there any evidence? I would say, yes it is. If you add more PO4, you get rid of GSA/GDA. If you add more NO3, you get rid of BGA, and if you add a lot of CO2, you get rid of BBA. But I don't have any scientific proof for that (that's the reason I said it's my hypothesis). Still, I would say that this hypothesis has more to it than your rigid statement that higher concentration of nutrients pose no risk for algae outbreak. I consulted this with quite a few algologists (incl. Roger W. Bachmann), and each one told me that it's nothing more than nonsense. Why we have no algae problems even under higher nutrients levels? Because we have huge number of plants (lowering the nutrient levels in water), good filtration, regular maintenance, weekly water changes, lot of algivores, and relatively low light levels. (But that's for a separate discussion.)
6) And my final question: What was your methodology for finding out the recommended amounts of nutrients for EI method? How did you get to 30 ppm NO3, 3 ppm PO4, 20 ppm K, and 0.5 ppm Fe (or so) per week? I never find any post of yours where you explain it in detail. Is it based on your subjective observations only, or do you have some serious data for this (and can you publish them)?
I'll be thankful to you if you can answer (at least some of) these questions.
Marcel


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## GHNelson (23 Nov 2014)

Hi 
You should be looking at around 20/25ppm this isn't set in stone though!
Increase your dosing level...... double dose!
Plants don't care if you over subscribe on the ferts...they will frown though if you under dose!
hoggie


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## pepedopolous (23 Nov 2014)

Thanks Hogan,

I thought I was already dosing 'unlimited' ferts and all problems were due to CO2. I have reduced light to <30 PAR and increased CO2 to the max I can manage with livestock.

To get 20 ppm in my 125l aquarium I would need to dose 80ml of my current solution daily or make a new solution of over 100g KNO3 in 500ml of water.

My plants must be junkies for NPK if this is what it will take to get them healthy!


Thanks again,

P


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## GHNelson (23 Nov 2014)

http://www.theplantedtank.co.uk/calculator.htm
Punch in the numbers!
Dose 10ml 3 x a week!
This calculation does not include the amounts used by plants and assumes there is no other source of nutrients.
It should be used as a guide only.
hoggie


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## pepedopolous (23 Nov 2014)

hogan53 said:


> You should be looking at around 20/25ppm this isn't set in stone though!


When you say 20/25 ppm do you mean with each dose or the total sum of 3 doses?
If the former than my numbers in the previous post still stand.
snapshot1 by pepedopolous, on Flickr
P


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## GHNelson (23 Nov 2014)

Dose 10ml 3x a week!
That will give you approximately 30ppm per week.
Remember there is other variables to take into consideration.
Your aquarium may have been set-up with tap-water which may have 5ppm - 50ppm Nitrate!
Plus your plants........ depending on your plant mass may eat 20 to 50ppm per week!
Then there is Nitrite converted to Nitrate....so all a tad estimated.
But your better over estimating than under dosing your tank!
I currently estimate that I have 100ppm Nitrate.... the plants don't care or the fish!
I do a huge water change with RO so that will remove at least 80ppm Nitrate!
Hope this helps to get your head around EI.
When dosing Co2 have a decent gas exchange on the surface!
hoggie


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## pepedopolous (23 Nov 2014)

Right... weekly!

Surely I can't be the only one not to see whether Tom Barr's 5-30 ppm NO3 is per single dose or per week (3 doses)?

The aquariumplantfood.co.uk recipe that I use currently results in 15.3 ppm PER WEEK. 

So I can increase each dose a little to get maybe 20-25 ppm.

LOL


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## GHNelson (24 Nov 2014)

Yes just double dose the aquarium plant food product!


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