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CO2 and EI

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.
 
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.
o2_test1_nano4.jpg

Here's a picture of this tank:
2014-10-18_1.jpg

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.

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.
 
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).


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. :cool:

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.

Center120_zps169e6b07.jpg

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.
 
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
 
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
 
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
 
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
 
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
 
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
 
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
 
Last edited:
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
 
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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