# amount of C02 required based on KH / mixing RO with tap water



## Paul195 (1 Jan 2018)

Hi

I asked the guy at the LFS about their planted tank, which is using RO water, and I noticed that they were injecting C02 at a very slow rate; something like 1 bubble every two seconds, whereas when I was using C02 previously, I was having to pump it in at something like 6-8 bubbles per second to achieve a 1 PH drop to get C02 levels right. My tank parameters are PH 8.4, KH 11, GH 13.

Could somebody explain the relationship between the the PH, KH  and the amount of C02 to reach the desired C02 levels please ?

Also, If I were to mix my current tap water with the above parameters,50/50 with RO, what would my resulting parameters be ? am I right in saying that my KH & GH would half ? what about PH ?

Thanks
Paul


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## Zeus. (1 Jan 2018)

Hi Paul
The relationship is simple and complex, depends on your understanding of chemistry

RO water has nearly everything stripped from it so it is more or less just water. (Distilled water is 100% pure) So when you add CO2 to it the [CO2] increases very fast so you dont need to add much to get the desired [CO2]. The reason is RO distill water has no (or very few buffers)
Tap water contains salts/minerals which act as buffers, so when you inject CO2 not all of it is available as CO2 for the plants it is buffered by the dissolved minerals.. So you have to inject more CO2 to get the same [CO2] as RO water.

Yes if you mix your tap water and RO as you suggest it would be about half, Your pH would be less.

But if you use 100% RO water controlling the [CO2] can be very tricky as you can go from ideal levels to toxic to livestock very quick. Where as Hard water (high Kh Gh) you will use LOTS more CO2 getting to your target pH.

I live in a hard water area and go though 6.5Kg of CO2 a month on my 500l tank. But I do have it at very high [CO2].

Very hard to compare one tank to another esp when talking BPS, mine is insanely high but it works well for me.

Hope that is of some help.

Zeus

I was going to put the graphs etc but I'm sure you have seen them, sometimes less is more


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## naz (1 Jan 2018)

I have extremly hard water living in the south east england,my kh is about 27 dkh,iv been in to the planted tank hobby for the last 15 years, always had a planted tank going in one way or another.Just use staight 100% ro water with a gh booster to keep the gh betweem 3 and 5 so you have some mag and calcium this is how i run all my tanks......and reap the rewards...


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## Paul195 (1 Jan 2018)

Thanks for both of your replies. Funnily enough Naz, this is the decision that have have just made after visiting the local fish store.

Could you recommend any specific product to remineralize with or are they all ok to get the job done ? I've heard a lot about equilibrium.

I am planning to take down my current tank and start from fresh with new substrate, plants and RO. To do this I will obviously have to house my current stock (1 SAE, 2 oddessa barbs, 2 dwarf neons, 4 otto cats) temporarily, and I'm a little confused about how to transition the the stock to the new tank. The guy in the LFS said that generally fish will fairly easily adapt to softer water, he said they have a hard time when put in harder water. With this said, I assume that I can't just take them out of my tap water and put them straight into remineralized RO water? Could I do this if I were to drip acclimatize them over the space of a few hours or would this need to be done over a longer period of time / using a different method ?

I have read that you can do it by just doing small partial water changes replacing with RO, but I'm a bit unsure when starting a new tank with 100% RO.


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## naz (2 Jan 2018)

hi paul
i use seachem equilibrium in all my tanks to raise the gh,i have a ro unit and i use 27l plastic containers that i fill up then i dose 3/4 tsp of equilibrium to the container then just take 27l of take water out and replace,this keeps my gh at about 3 degrees then i dose fert once a week a water change.

i would just drip acclimatize them over a period of 2 hours or so and thay will be fine,this is how i do it.


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## Zeus. (2 Jan 2018)

Also the size of the tank may be a limiting factor, I have over 250l to change a week, thats a lot to store and treat. RO wise it would cost a fortune in water. So I just accept the hard water and deal with it


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## ceg4048 (4 Jan 2018)

Paul195 said:


> Hi
> 
> I asked the guy at the LFS about their planted tank, which is using RO water, and I noticed that they were injecting C02 at a very slow rate; something like 1 bubble every two seconds, whereas when I was using C02 previously, I was having to pump it in at something like 6-8 bubbles per second to achieve a 1 PH drop to get C02 levels right. My tank parameters are PH 8.4, KH 11, GH 13.
> 
> ...


Hello,
        The amount of CO2 needed to be injected in order to reach a certain amount of dissolved CO2 is exactly the same whether using pure RO, a mix of RO/tap, or pure tap.
CO2 does not care about the alkalinity of the water. Only three things determine the solubility or retention of CO2 in water:
Temperature, Pressure, Salinity.

Having said that, it's necessary to understand that in water having a high alkalinity versus RO water, the pH changes that result from injecting the same amount of CO2 will be different. This difference is caused by the higher alkalinity which resists a change in pH. In fact, this is by definition, what alkalinity is. If you add the same amount of acid each to a sample of RO water, RO/tap and to a sample of KH 11 water the same amount of acid will enter the water, obviously, but the ph drop in KH 11 water will be slight. The pH change in the RO/tap water will be moderate and the pH change in the RO water may register as very large.

In our case, the acid that we are adding is a weak acid called Carbonic acid, which is formed when CO2 comes into contact with water. It is unavoidable and is complicated, however, it's only necessary to understand the different _behavior _of pH when acid comes into contact with the various types of of water.

Also, you cannot really compare your LFS system with your own. Their injection pressure may be high, for example, set by their regulator working pressure. The temperature of their water may be different. The tank may be more tightly covered and may retain more CO2.  Their injection method and flow/distribution in the tanks may be different, so it's really difficult to compare tank to tank.

If you cut your tap with 50% RO, then KH and GH would halved, but it is unclear by how much the pH would change.
pH is a logarithmic calculation. KH and GH are linear (proportional) calculations.

In any case, it is unimportant what the pH of the RO/tap mixture is. _It only matters what the change in pH is when you add the CO2._
That is the information you look for when trying to determine whether you are adding enough CO2.

If your resulting KH is around 4-6, then you can aim for a 1 unit pH drop. If the KH is higher due to using a greater percentage of tap then the pH drop when adding the same amount of CO2 will be less.

Hope this helps.

Cheers,


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## Paul195 (4 Jan 2018)

Hi

Thanks for the detailed explanation. That explained my question perfectly.


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## Cor (5 Jan 2018)

ceg4048 said:


> If your resulting KH is around 4-6, then you can aim for a 1 unit pH drop. If the KH is higher due to using a greater percentage of tap then the pH drop when adding the same amount of CO2 will be less.


So the 1 point pHdrop method is only accurate at a KH 4-6?


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## Edvet (5 Jan 2018)

Aye, i used a 1.5-1.6 drop in softer water.


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## sciencefiction (5 Jan 2018)

Additionally to what was already said, the effect of CO2 on KH is so little, in practice it has no effect whatsoever.


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## HiNtZ (6 Jan 2018)

Zeus. said:


> Hi Paul
> The relationship is simple and complex, depends on
> I live in a hard water area and go though 6.5Kg of CO2 a month on my 500l tank. But I do have it at very high [CO2].
> 
> ...



6.5kg A MONTH?? Jesus!

I do 5kg in 6 months with a BPS of 10-12 on my 155L GH6 KH4. Same as you though really, my tank requires massive amounts to get slightly above average levels. Everyone else I know on CO2 seems to get away with 3-4 bps on similar sized tanks.... but their light is way way weaker than mine. 

My CO2 also comes on 5 hours before lights on.


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## Edvet (6 Jan 2018)

I did 10 kg/6 weeks in my big tank


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## Zeus. (6 Jan 2018)

I was concerned about the amount of CO2 I was using, until Clive informed me that he was using a 22Kg clyinder every 5-6weeks on his 700l tank.

Sent from my Moto G (4) using Tapatalk


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## Paul195 (21 Jan 2018)

ceg4048 said:


> The amount of CO2 needed to be injected in order to reach a certain amount of dissolved CO2 is exactly the same whether using pure RO, a mix of RO/tap, or pure tap





ceg4048 said:


> In any case, it is unimportant what the pH of the RO/tap mixture is. _It only matters what the change in pH is when you add the CO2._



I thought I was clear about this but it turns out I'm not! I understand that the KH will affect how much the PH drops due to the buffering capacity (small swings in high KH, larger swings in low KH).

Are you saying that if you inject at "X" rate no matter what your KH is, then the same amount of CO2 will be dissolved in the water, the only difference being the amount that the PH changes by ? in other words the KH has no bearing on how much CO2 you need to inject, it only affects the amount of PH you need to drop by to achieve optimum levels ?

Does the starting PH of your water before adding any CO2 have any bearing on the amount of CO2 required ? I am keen to try to understand why the amount of CO2 people add varies so much.



ceg4048 said:


> Also, you cannot really compare your LFS system with your own. Their injection pressure may be high, for example, set by their regulator working pressure. The temperature of their water may be different. The tank may be more tightly covered and may retain more CO2. Their injection method and flow/distribution in the tanks may be different, so it's really difficult to compare tank to tank.



If I wanted to make my CO2 last longer, am I right in saying the only ways to do this are by lowering the temp of the water, fitting a lid, and ensuring flow and distribution is optimal, and water parameters have no part in this ?

Hoping somebody could clarify for me...

Many thanks

Paul


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## dw1305 (22 Jan 2018)

Hi all,





Paul195 said:


> Does the starting PH of your water before adding any CO2 have any bearing on the amount of CO2 required ?


I'm not a CO2 user (or a chemist), but I think the answer is that a one uit pH drop gives you about 30ppm CO2 what ever the initial pH and dKH readings were. 

There is an explanation in <"Question about pressurised...">.

cheers Darrel


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## Edvet (22 Jan 2018)

dw1305 said:


> I'm not a CO2 user (or a chemist), but I think the answer is that a one uit pH drop gives you about 30ppm CO2 what ever the initial pH and dKH readings were


Not sure about this
1) pH is a logarithmic curve, so ad lower pH you'll need to add more to get the 1 point drop
2) CO2 giving the acid rection (H2CO3) can be buffered by higher carbonate and bicarbonate values, thus needing higher values to get the 1 point drop in "hard"water


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## ian_m (22 Jan 2018)

Below is the a table (from Barr Report) that shows pH vs kH and resulting/caused by ppm of CO2.

Thus, for example, your initial water has a kH of 4 and pH of 7.6. If you drop the pH by 1 to 6.6, by injecting CO2 the ppm increases to 30ppm.
Similarly for water of 16kH, with initial pH of 8.2, dropping pH to 7.2 the CO2 is similarly 30ppm.
Thus you see 30ppm produces an approximate 1pH drop.

This should be taken "roughly" of course, as the chart below assume pH is solely driven by kH value and CO2 value. In a real tank there are other buffering chemicals other than carbonate and other acids/alkalis present affecting pH values. Generally though I think you get an under read ie 1pH drop caused by less than 30ppm, meaning at least you don't gas your fish. A drop checker can help out here as it is only affected by CO2 ppm and not anything else in the tank water.


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## dw1305 (22 Jan 2018)

Hi all, 





Edvet said:


> 1) pH is a logarithmic curve, so as you lower pH you'll need to add more to get the 1 point drop


Ed I'm not sure, it is back to needing a chemist, but think it is because pH is a log10 scale, and if you plot an exponential curve as log10 values you get a straight line.

It is this bit and links (from <"Question about pressurised CO2....">





dw1305 said:


> ..... But I think I've got it.
> 
> Assuming that the _"pH drop of 1_" for ~30ppm CO2 is right, it is because it is a buffered system, and pH is a log10 scale. The drop in pH is determined only by the concentration of CO2 in the water.
> 
> ...


cheers Darrel


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## AverageWhiteBloke (22 Jan 2018)

Paul195 said:


> If I wanted to make my CO2 last longer, am I right in saying the only ways to do this are by lowering the temp of the water, fitting a lid, and ensuring flow and distribution is optimal, and water parameters have no part in this ?



Yeah you could do all that, some also say that misting the tank has benefits rather than fully dissolving the co2 in the water. The small bubbles cling to plant leaves and get absorbed directly through the leaf. A lot of people don't like the mist this causes including myself but I tend to have the majority of the injection phase going on while I'm at work so I don't have to look at it. By the time I get in and had my tea and a scrub up the co2 injection is nearly over and I can view the tank as nature intended 

The other option is the lighting, I'm guessing that kit you have there has some level of control. The 30ppm figure or 1 drop in PH is like the drop checker, not an absolute but a general rule of thumb figure that people in the planted tank community have decided to be a indication that there should be sufficient co2 available for plants and bordering on being unsafe for fish. You have to use it at some discretion as with the DC it tells you in that particular area of the tank a couple of hours ago there might have been enough co2. Similarly measuring ph of water which should be done in the tank as the gas has already left or leaving if you take out a sample will only tell you what the levels are in the upper rich co2 water level as the gas is just about to escape into the atmosphere of which 90% will.

If you want to conserve gas then controlling the lighting is the key. Having too much light in either duration or intensity will increase the demand for co2. The lights set the pace and you need to try and match that with your injection. It's fair to say that there are many beautiful slow growing plants in the hobby that if not given too much light can get away without having to use added co2 at all. In fact some of these plants prefer you not to accelerate growth too far as the longer the same leaves are in the tank the more susceptible they are to growing algae on them. Faster growing stems etc people tent to trim off the leaves more often before algae gets the chance to coat them.

What I tend to do these days is keep the tank lighting minimal for a while so's not to push the plants too hard and induce deficiency then giving the algae the advantage over weak plants. Add a bit of co2 for a few weeks, the plants will surely love that. If you feel confident then maybe knock the lights up a setting or another half hour with a slight increase in co2. That's why it is difficult to second guess anybody's tank, they all act differently depending on so many factors, even the plant mass changing will affect co2, it might be right when you setup but as the tank fills with plants there will be less flow and more co2 uptake. Simply giving the plants a good clip out can bring things back inline before having to turn that co2 wheel.

I wouldn't get too stuck on the 30ppm, it's not that accurate and maybe your tank doesn't even need it depending on the other factors. Its all about finding what your particular tank needs and trying to maintain stability at that. For instance any time I managed to get a 1 ph drop in my tank the fish didn't like it and gasped at the surface. I love a dense planted tank but not to the point of stressing fish out. I try to aim for a balance in there where flora and fauna are happy and complimenting each other. Excessive lighting can tip the scales and you'll find yourself chasing your tail which takes some of the shine off the hobby IME.

Just to add I wouldn't bother mineralising either, just cut your existing water with RO if you want to soften it down. Mineralising RO is just another tail chaser which will have you chasing more hypothetical numbers.


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## Edvet (22 Jan 2018)

AverageWhiteBloke said:


> just another tail chase


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## AverageWhiteBloke (22 Jan 2018)

Haha, finally the dog got it. Don't get me wrong, I like to understand the numbers and what they mean but often I find people will chase numbers and miss the wood in the trees. I think my reasoning changed when I had an instance where I was away from my tank for an extended period with no intervention from me, no lighting other than from a window or filtration or dosing (fair enough it was in summer) After 5/6 weeks the tank looked OK as it happened, algae was at a minimum as the algae eaters hadn't been fed and in fact had started to make a start on the plants. Plants were a bit on the weedy side but still looking good.

Got me thinking, if this tank can get by on its own, is there any reason why I should obsessively be dosing at the same time everyday measuring to the mil and chasing co2 and ph numbers and still run into issues now and again. Over accelerating growth through lighting just brings in a load of problems you can do without. It's like running on the ragged edge, one slip in cleanliness, flow, nutrients or co2 and a problem is waiting to jump on you. I went forward with a new approach, put SOME light over a tank and watch the plants. No signs of co2 or nutrient related issues and new growth on the plant and maybe chance my arm with a touch more light. Then the options are some co2 and more ferts or leave the lights alone. Keep doing this incrementally without rushing things while plants adapt to the changes and find where I personally want to be which is low maintenance and healthy plant growth. I'm not really bothered if I have 80% of my lights left to use, its there if I ever fancy it and it keeps my leccy bill down 

Steady growth for plants in my experience grows a better formed all round better looking plant. Most people will put some plants in and before they have even had chance to put some roots down throw everything including the kitchen sink at them and spend the next six months in the forum algae fighting in denial that this can't be happening because my co2 is 30ppm, DC is lime green, they are dosing more ferts than ever could be used and the lighting puts out more power than Blackpool in November.

Problem is the plants don't visit this forum and very rarely do as they're told.


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## AverageWhiteBloke (22 Jan 2018)

I guess in conclusion, it's best to let the plants tell you what they want instead of you telling the plants what they should get maybe.


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## Edvet (22 Jan 2018)

AverageWhiteBloke said:


> let the plants tell you what they want


So patience and observation


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## dw1305 (22 Jan 2018)

Hi all,





AverageWhiteBloke said:


> Steady growth for plants in my experience grows a better formed all round better looking plant.


That one. Good things come to those who wait.





AverageWhiteBloke said:


> Problem is the plants don't visit this forum and very rarely do as they're told.


I blame the plants as well, they won't read , or do what you tell them to do, and they have  <"moved the goal-posts">.





Edvet said:


> So patience and observation


Quality. 

cheers Darrel


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## ceg4048 (22 Jan 2018)

Paul195 said:


> Are you saying that if you inject at "X" rate no matter what your KH is, then the same amount of CO2 will be dissolved in the water, the only difference being the amount that the PH changes by ? in other words the KH has no bearing on how much CO2 you need to inject, it only affects the amount of PH you need to drop by to achieve optimum levels ?


Yes. Exactly.


Paul195 said:


> Does the starting PH of your water before adding any CO2 have any bearing on the amount of CO2 required ? I am keen to try to understand why the amount of CO2 people add varies so much.


No.
The reason for the variance is because no two hobbyists or tanks are identical. Temperature is different, pressure is different, injection technique is different, flow/distribution is different, lighting is different, plant mass and plant species are different.

Many people blame their KH for their CO2 failures. This is a self induced hypnosis. They fail as a direct result of their poor CO2 injection techniques and they compare their tank's water parameters with their neighbor's tank, which you should never do. It is estimated that over 90% of the failures in planted tanks are a result of poor CO2 techniques.


Paul195 said:


> If I wanted to make my CO2 last longer, am I right in saying the only ways to do this are by lowering the temp of the water, fitting a lid, and ensuring flow and distribution is optimal, and water parameters have no part in this ?


Yes. 
By doing so you you improve the efficiency and retention of the gas in water. Additionally, you can reduce the intensity (not necessarily the duration) ogf the light striking the plants. This will reduce their demand for CO2 but will also slow their growth rate, which is actually a good thing because it means less organic waste ejected in the tank. Less lighting intensity also reduces the demand for nutrition.

As I mentioned before, there are only three water parameters that have an effect on CO2 dissolution in water; Temperature, Pressure and Salinity. All other parameters are irrelevant.

Cheers,


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## Paul195 (23 Jan 2018)

ian_m said:


> Thus, for example, your initial water has a kH of 4 and pH of 7.6. If you drop the pH by 1 to 6.6, by injecting CO2 the ppm increases to 30ppm.
> Similarly for water of 16kH, with initial pH of 8.2, dropping pH to 7.2 the CO2 is similarly 30ppm.
> Thus you see 30ppm produces an approximate 1pH drop.


My PH is 8 and my KH is 4. this equates to 1.2ppm. Ceg mentioned previously that if I have a KH of around 4-6 then I could aim for a PH drop of 1. But according to the chart, dropping 1 point to PH7 would only provide 12ppm CO2. According to the chart I would need to drop to 6.6 from 8 to get 30ppm.

According to the chart, If my PH is 8 and my KH is 4, this equates to 1.2ppm. If my PH is 7 and my KH is 4, this equates to 12ppm. The way that I have been interpreting the chart is that at the particular KH of your tank water, the starting PH of your water decides how much CO2 is present before CO2 addition, and if you start with a PH of 7 you would already have 12ppm and would only need to drop from 7 to 6.6 to get the magic figure. If this is the case and 12ppm was already present, surely less gas would be needed to add the additional 18ppm than would be required at PH8 where you would need an additional 28.8ppm ?

Sorry... still confused


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## AverageWhiteBloke (23 Jan 2018)

The initial measure before injection doesn't mean that's how much co2 is in the water to start with. It's a measure of the bases and acids. Some of it could be co2 but with good surface agitation there will be very little co2 present.

Sent from my STH100-2 using Tapatalk


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## dw1305 (23 Jan 2018)

Hi all, 





Paul195 said:


> My PH is 8 and my KH is 4


It is a bit strange, but carbonates are insoluble in pure water, but soluble in acids (proton donors). If you don't have any bases (proton acceptors) present, other than carbonates, the pH of the water is dependent upon the CO2(H2CO3) ~HCO3- ~ CO3 equilibrium, and the amount of H2CO3 (carbonic acid) present relates to the 400ppm of CO2 in the atmosphere.  The theoretical amount of dissolved CO2 is about 0.5ppm, and only a minute proportion of this becomes H2CO3.  

This equilibrium is stable at pH8, and water with any carbonate content will read ~pH8.  There is a more complete discussion at <"Aquasoil pH increase">.

cheers DarreI


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## ceg4048 (23 Jan 2018)

Paul195 said:


> Sorry... still confused


As I and others have mentioned repeatedly, you cannot use the chart to determine how much CO2 is in your water. The Chart represents a mathematical relationship between the pH, the Carbonate Hardness (amount of carbonate) and the CO2.

Because this chart is basically an Excel spreadsheet of  the equation mentioned by Darrel it cannot represent anyones water unless that water is prepared in accordance with the data used to build the chart.
The chart makes the following assumptions;
1. That the only acid in the water is Carbonic acid.  - This is never true in a tank or in any natural body of water.
2. That the only source of alkalinity in the water is Carbonate ion. - This is only seldom true as there are many possible substances which contribute to alkalinity.
3. That you are able to accurately measure Carbonate Hardness - This is also rarely true as hobby grade test kits cannot tell the difference between Carbonate and other alkaline substances.

As AWB mentions, the way to use the chart is to use the differences between a starting value and the target value in order to determine the change in CO2. The chart will not help you to determine absolute values, and neither is it necessary to know those values. But, if you change your CO2 by 20 ppm, or by 30 ppm, or by whatever target amount, then that is a good enough estimate. Use these estimates in conjunction with your dropchecker to ensure that the estimate is in the safe zone.

Cheers,


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## AverageWhiteBloke (23 Jan 2018)

That's why it's called a "drop check" Paul, you're measuring the drop to calculate how much co2  you now have compared to before injecting based on the assumption that before you started injecting there wasn't any. (Or very little, not worth bothering about)

There could have been if the gas from the previous day hasn't gassed of through lack of surface agitation or scum on the water effectively sealing it in or trapped in the filter but rarely.

That's where the drop checker solution comes in, the parameters Clive was talking about which would make that spread sheet chart work is a solution where the only source of alkalinity is carbonate ion and distilled water made up to 4dkh. It's isolated from the tank water so doesn't care what your other tank parameters are, also isolated from any acids of any kind that may be in your tank water so effectively the only thing that can get in there is gas. Because co2 is acidic the gas that gets in there will acidify the water and change the colour of the PH fluid. General rule of thumb, lime green about right. Yellow bit much and blue not enough. 

Both the above techniques have their downfalls as pointed out in previous posts, but you can use both techniques and correlate your findings to give you a ball park idea of where you are regarding co2.

That's why I said earlier on not to get too bogged down with the numbers as neither are that accurate but the best we have for now. Co2 issues can still show in plants even with good colours and numbers if the flow isn't right. 



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## AverageWhiteBloke (23 Jan 2018)

Just to clear up another point Paul in case you were wondering, when you do the PH drop using a ph pen and kh test the PH pen will measure other acids and bases of course and as Clive pointed out the KH test will also measure other things other than carbonates. That's why the pre injection test is insignificant and just a start value to work from. Because you are dealing with a short period of time, usually a few hours between co2 on and lights on it is assumed that the water parameters haven't changed since the first test other than the co2.

As you can see, lot of assumptions, mixed with time delays, test kits that aren't that accurate, and  only measuring one particular point at one particular time and ph fluid colour being affected by the lighting. No need to be trying to get within 2ppm if you want to keep your sanity 

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## Zeus. (23 Jan 2018)

My starting pH when CO2 comes on varies throughout the week, then changes big time after water change, but the CO2 injection rate is constant. Some days the drop is 1.2pH others it's 1.5pH, but who's pH controler or pen is accurate anyway. DC is normally light yellow.

Nice thing about pH controler is the probe is on a lead so the probe can be moved anywhere in tank not just the surface, which is helpful IMO

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## AverageWhiteBloke (23 Jan 2018)

Indeed, obviously the Drop Checker can be moved about as well. I was going to get one of those Seneye things at one point so I could get readings from anywhere in the tank but unfortunately it only logged ph down to 6.4 and with my very soft water it wasn't low enough. 
I was talking to one of the sales heads from Seneye who was saying that later this year they are bringing out a planted tank version but it was still in production. I suggested PH should  be able to go lower than 6.4 for the soft water people and he said he would pass that on to the team so you never know.

Again though, Whatever we get the plants will always tell you more. I'm free from co2 madness for now, just running a low tech although I will be getting back into it soon. I'm finding if you have dimming it's far easier to mess with lighting than all the other stuff but then again I keep planted tanks and fish as a hobby long term rather than temporary show stoppers.





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## Paul195 (24 Jan 2018)

Many thanks to everybody who has posted to help me try to understand this.

I already have a drop checker installed, I was mostly trying to understand the way that the chart works (point taken that is only an estimate and should be used in conjunction with the DC). 

Ok so to summarize....

1. Find the KH of your water
2. Find out what PH corresponds to the level of CO2 you are trying to achieve (usually 30ppm)
3. Drop to that PH value from whatever the PH of your water is before injection.
4. Cross reference with the drop checker to check the colour is lime green (or in some cases slightly yellow)

Correct ?


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## AverageWhiteBloke (24 Jan 2018)

Paul195 said:


> Many thanks to everybody who has posted to help me try to understand this.
> 
> I already have a drop checker installed, I was mostly trying to understand the way that the chart works (point taken that is only an estimate and should be used in conjunction with the DC).
> 
> ...


By jove, I think he's got it  nice one pal haha. It it can boggle your mind at times. I often find things in growing plants turn out to be the exact opposite of what would seem logical.

Last point would be, after all that, just remember the drop checker has a delay so the real time reading you take with the pen will roughly match up with the DC in about an hour or so time. Plus, just to make things a bit more interesting. The DC only measures in that particular area of the tank, likewise the PH pen only measures the top layer as the gas is leaving the tank. The plants will have the final say. If you have plants that are showing signs of co2 issues then you have bad flow in that area regardless of what the PH pen and DC are saying.

90% of the gas you inject doesn't even end up in the plant, the gas wants to get out of the tank as fast as possible in warm water and play in the atmosphere with all the other gases. Look at it like this. If 100 co2 atoms go past a plant it can only grab 10 of them (ball park for simplification) with high lighting the plant is going to need all it can get hold of. If you have an area of the tank with little co2 but getting bashed with the same high light it isn't even going to grab the 10=co2 related plant issues. Even if the DC is a nice colour and the pen is telling you what you want to hear.

If you suspect you have a place of poor water movement the gas isn't getting to,  resolve that by altering spray bars and outlets or pumps whatever. That place is a good place to put your drop checker, if things look good there chances are the rest of the tank is good to. 

Enjoy injecting gas haha it's a bit like rubbing your belly while rubbing your head with the other.

Then the plant mass will change or you have more surface agitation when water levels drop and it all changes again.

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