CO2 - How much is needed? - The Planted Tank Forum
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post #1 of 32 (permalink) Old 07-05-2016, 08:07 PM Thread Starter
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CO2 - How much is needed?

Generally we tell people starting with CO2 that they should get 30 ppm of CO2 into the water - that's what the plants need. This is not good advice!

Tropica has a pretty good, brief article on this subject: Fertiliser and CO2 for your aquarium. - Tropica Aquarium Plants This article says "A bit of CO2 (e.g. 3-5 mg per L) is better than nothing. Plants that are marked "Medium" require about 10-15 mg CO2 per L, but "Advanced" plants require 15-30 mg CO2 per L." (mg per L is the same as parts per million, or ppm) I would modify this quote by saying the amount of CO2 that is best depends on the amount of light you are using. With low light the plants will show improvement with about 3-5 ppm or more, with low medium to medium light they will show much improvement with 10-15 ppm or more, and with high light they will show much improvement with 30 ppm or more.

I have about 30-35 PAR light intensity, good low light, and had very unimpressive growth of my plants, using only Excel (Metricide) as a carbon source. I added a DIY CO2 system along with the Excel, and now the plant growth is much improved, although still slow. My drop checker, using 1 dKH water in it, indicates that I most likely have about 3-10 ppm of CO2.

Using Excel along with DIY CO2 reduces the threat of BBA attacks caused by the variable amount of CO2, and lets the plants grow faster due to the greater availability of carbon. Using such low ppm of CO2 eliminates any threat of harming the fish with the CO2, makes the CO2 last a lot longer, and is much easier to keep reasonably constant.
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post #2 of 32 (permalink) Old 07-05-2016, 11:09 PM
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Yup, I was binging on Tropica videos the other day and all their tanks are around 25mg/L (ppm) CO2.

You can probably bump up the PAR to get better growth. This is not a new idea but what about a constant low CO2 24/7 which DIY yeast provides? Those with CO2 tanks could probably do 15-25ppm safely for 24/7.
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post #3 of 32 (permalink) Old 07-05-2016, 11:21 PM
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Originally Posted by Hoppy View Post
My drop checker, using 1 dKH water in it, indicates that I most likely have about 3-10 ppm of CO2.
Hi Hoppy,

I know that a 4.0 dKH indicator solution is standard for drop checkers so we can use the standard PH scale to determine PPM (PH 6.6 color = 30ppm). How do you do the math with 1.0 dKH water indicator solution or are you using something like this chart?


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post #4 of 32 (permalink) Old 07-05-2016, 11:46 PM
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I have about 30-35 PAR light intensity, good low light, and had very unimpressive growth of my plants, using only Excel (Metricide) as a carbon source. I added a DIY CO2 system along with the Excel, and now the plant growth is much improved, although still slow. My drop checker, using 1 dKH water in it, indicates that I most likely have about 3-10 ppm of CO2.
I got to say that despite varying opinions against, excel is not a source of C. its a sterilizer. I have this engrained in my head. When overdosed it'll cause some Shiz to happen, and overdosed can also very well melt or kill a plant. Someone then explain to me this: with excel how many ppm's C are you adding? With co2, how come you can overdose and not have the same ill effects? stunting i'd say vs obliterating the plant.

For the rest light and co2 and o2 seem to correlate better than any dosing schedule regime in having a successful tank.
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post #5 of 32 (permalink) Old 07-06-2016, 12:40 AM
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I got to say that despite varying opinions against, excel is not a source of C. its a sterilizer. I have this engrained in my head. When overdosed it'll cause some Shiz to happen, and overdosed can also very well melt or kill a plant. Someone then explain to me this: with excel how many ppm's C are you adding? With co2, how come you can overdose and not have the same ill effects? stunting i'd say vs obliterating the plant.

For the rest light and co2 and o2 seem to correlate better than any dosing schedule regime in having a successful tank.
Hi StrungOut,

Good questions! Yes glutaraldehyde, the main ingredient in Seachem Excel is a sterilizer. And you are correct, it can cause issues when overdosed in a tank with plants, fish, shrimps, etc. Seachem Excel / glutaraldehyde does not add any ppms of CO2 to an aquarium but it does make carbon molecules available to plants for use in photosynthesis.

There are several chemical formulas for glutaraldehyde such as CH2(CH2CHO)2. All of the formulas show the existence of carbon molecules (the "C"'s in the formula) in the solution. Tom Barr explained it to us in his talk at GSAS in 2010. Basically Dr. Barr (yes he has his doctorate) explained the similarity of the glutaraldehyde molecule to molecules manufactured during the Calvin Cycle of photosynthesis allows the glutaraldehyde to provide its carbon molecules and enhance the productivition of sucrose, the building block that plants use for growth.

For the biochemists out there Seachem did a paper on the subject many years ago. In it they state:
Quote:
The chemical structure of Flourish Excel™ is quite similar to some of the products of photosynthesis such as Ribulose 1,5-bisphosphate and 2’-carboxy-3-keto-D=arabinitol 1,5 bisphosphate. Flourish Excel™ possesses the same basic 5-carbon chain seen in these molecules.
which is what Tom Barr explained to us non-biology majors in terms we could understand.

I'm sure I did not explain it as well as Tom Barr could, maybe he will weigh in if he gets a chance.
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post #6 of 32 (permalink) Old 07-06-2016, 01:28 AM
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I got to say that despite varying opinions against, excel is not a source of C. its a sterilizer.
I've always kinda felt the same way. Even though it's marketed as a nutrient and has the secondary effective of being an algaecide, I feel it's the other way around. Has anybody actually setup two identical tanks and seen the difference with and without Excel.
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post #7 of 32 (permalink) Old 07-06-2016, 01:37 AM
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Originally Posted by Seattle_Aquarist View Post
Hi StrungOut,

Good questions! Yes glutaraldehyde, the main ingredient in Seachem Excel is a sterilizer. And you are correct, it can cause issues when overdosed in a tank with plants, fish, shrimps, etc. Seachem Excel / glutaraldehyde does not add any ppms of CO2 to an aquarium but it does make carbon molecules available to plants for use in photosynthesis.

There are several chemical formulas for glutaraldehyde such as CH2(CH2CHO)2. All of the formulas show the existence of carbon molecules (the "C"'s in the formula) in the solution. Tom Barr explained it to us in his talk at GSAS in 2010. Basically Dr. Barr (yes he has his doctorate) explained the similarity of the glutaraldehyde molecule to molecules manufactured during the Calvin Cycle of photosynthesis allows the glutaraldehyde to provide its carbon molecules and enhance the productivition of sucrose, the building block that plants use for growth.

For the biochemists out there Seachem did a paper on the subject many years ago. In it they state:
which is what Tom Barr explained to us non-biology majors in terms we could understand.

I'm sure I did not explain it as well as Tom Barr could, maybe he will weigh in if he gets a chance.
You got a link? I'd like to actually hear it from him myself lol my bad Roy

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I've always kinda felt the same way. Even though it's marketed as a nutrient and has the secondary effective of being an algaecide, I feel it's the other way around. Has anybody actually setup two identical tanks and seen the difference with and without Excel.
Yes even though what Roy stated, I don't see it

I don't see plants taking it in and respirating o2 that way.

All I can say and seen it done is that it tackles destroys algae.
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post #8 of 32 (permalink) Old 07-06-2016, 05:28 AM
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Quote:
Originally Posted by Hoppy View Post
Generally we tell people starting with CO2 that they should get 30 ppm of CO2 into the water - that's what the plants need. This is not good advice!

Tropica has a pretty good, brief article on this subject: Fertiliser and CO2 for your aquarium. - Tropica Aquarium Plants This article says "A bit of CO2 (e.g. 3-5 mg per L) is better than nothing. Plants that are marked "Medium" require about 10-15 mg CO2 per L, but "Advanced" plants require 15-30 mg CO2 per L."
I am not trying to be contrarian, nor defend/attack anything or anybody. I just want to provide a different perspective. All the respect Hoppy for your experience, knowledge and interesting comments and topics.

I feel we could argue the same for every nutrient recommended level. Few aquariums need 3ppm PO4 weekly. Furthermore, what one aquarium needs today might not be the same as tomorrow or after a big trim. I will still recommend this level, provide it all the time as there is nothing wrong with a little extra with the 50% wc. Always changing it increases the likelihood of running into deficiencies.

Then, the word need is not very precise. My aquarium can survive with 2ppm PO4, but it does a lot better with 4ppm PO4. Which level is needed ?

I use PO4 for my arguments as CO2 is even more problematic. I think most of us had aquariums where the KH/pH chart gave us large overestimation of our CO2 levels, other where the indicator turned yellow but algae/plant problems were solved with extra CO2. If your measuring tool says you have 30ppm, add a very large confidence interval around it.

CO2 is also very variable at one time-point in different places of aquarium. Water that has 60ppm at the exit from the reactor could end up with 15ppm at filter intake after passing through plants and surface layer. How, when, where is the measurement to be done to get an accurate estimation of 30ppm is often a problem for newcomers.

As you rightly point out, light is the main driver of CO2 demand. However things are not as easy as only looking at light levels at the ground. Plants' needs also vary across the height of the tank... shaded bottom layer is ok with less, the nearer the light the more CO2 needed. Same light and aquarium, one aquascape can have lower CO2 as it is mostly grass; the other needs more because R. macrandra will get damaged near the light. Which of these CO2 need levels should be targeted as a general advice ?

Is there any limitation in the tank ? Less CO2 is ok then. Tom Barr even argues that low PO4 could help reduce plant problems in tanks that would be CO2 limited.

Like all the nutrients, C needs to be provided in non-limiting amounts for good plant growth. If you are unable to provide this level (no matter the reason) the best way forward is to reduce the light intensity. A large number of plants can survive and grow at lower light intensities. What exact ppm is non-limiting depends on your specific aquarium and point in time. For this reason I consider it good advice to recommend 30ppm for non-limiting CO2 levels in medium-high light setups.

Further reading: The light limiting growth management method - Aquarium Plants - Barr Report

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post #9 of 32 (permalink) Old 07-06-2016, 03:44 PM
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Having just started a DIY CO2 system in my dirted 20 gallon tank, it's undersized for a reason. The soil is supposedly a source for CO2.

But since I also grow plants that a water column feeders, I think a supplemental source of CO2 seems to be working well. One thing about DIY CO2 with yeast and sugar is that the output is temperature and age dependent. As the yeast culture warms the output increases and as it ages the output slows. I used to put my DIY CO2 bottles over my light ballasts so they would warm up as the ballasts warmed, which bumped the CO2 output a small amount to catch up with the light.

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post #10 of 32 (permalink) Old 07-06-2016, 04:01 PM
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Hi All,

It's funny that @dukydaf should mention Tom Barr's 'Light Limiting Growth Method', that was the exact presentation Tom Barr was making to GSAS when he discussed the Calvin Cycle and how glutaraldehyde can provide additional carbon atoms/molecules. On a side note, he also explained that the 'pearling' we see on our plants was not the result of plants 'breaking down' CO2 into oxygen but rather it was the plants 'breaking down' water to generate the O2 bubbles....it was an excellent talk and I revisit it regularly as part of the GSAS video library.
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post #11 of 32 (permalink) Old 07-07-2016, 01:03 AM Thread Starter
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Hi Hoppy,

I know that a 4.0 dKH indicator solution is standard for drop checkers so we can use the standard PH scale to determine PPM (PH 6.6 color = 30ppm). How do you do the math with 1.0 dKH water indicator solution or are you using something like this chart?

You don't have to do the math - the chart works fine. Note that at 1 dKH, you start getting green at about 3 ppm of CO2 and you start getting near yellow at about 12 ppm. With a tank full of green plants (and, sometimes, algae) it is hard to determine exactly how green the drop checker water is (although the best drop checkers make it a lot easier), so there is a fairly wide range of possible CO2 ppms for "green". But, it is sufficiently accurate to determine that you are, in fact, raising the CO2 level in the water with the DIY CO2 you are using.

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Someone then explain to me this: with excel how many ppm's C are you adding? With co2, how come you can overdose and not have the same ill effects? stunting i'd say vs obliterating the plant.
It doesn't matter how many ppm of C you are adding. Any planted aquarium will have lots of C in it - the plants are a big "source" of C, for example, as are the fish. What the plants need is bioavailable C, which can be in the form of CO2, which the plants evolved to use, or a chemical like glutaraldehyde, which fortuitously the plants can get C from.

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post #12 of 32 (permalink) Old 07-07-2016, 01:16 AM Thread Starter
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Has anybody actually setup two identical tanks and seen the difference with and without Excel.
Yes, although I can't link to any writeups about it. Many of us have done the equivalent experiment by adding Excel to a low light tank that had plants barely growing, and saw a significant increase in the growth rate. I have also then doubled the Excel dosage from 1 ml per 10 gallons of water to 2 ml per 10 gallons, and saw another significant increase in the growth rate. When I used a higher dosage I didn't see nearly as much improvement, but did see a lot more damage to vals. I don't think there is any reason to doubt that Excel works.
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post #13 of 32 (permalink) Old 07-07-2016, 05:53 AM
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Yes, although I can't link to any writeups about it. Many of us have done the equivalent experiment by adding Excel to a low light tank that had plants barely growing, and saw a significant increase in the growth rate. I have also then doubled the Excel dosage from 1 ml per 10 gallons of water to 2 ml per 10 gallons, and saw another significant increase in the growth rate. When I used a higher dosage I didn't see nearly as much improvement, but did see a lot more damage to vals. I don't think there is any reason to doubt that Excel works.
Low tech, low schmeck. Do it in a high light tank, the excel will get the plants no where, where pressurized co2 or diy whichever will.

Correct me if i am wrong.

In a low tech tank there are more variables and room for screw ups. The "excel" eliminated whatever algae is left hence better plant grow.

Do it with high light, excel only see how much you can put in and so on and see where your plants are at.

Thesess are bold statements
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post #14 of 32 (permalink) Old 07-07-2016, 06:24 AM
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When people refer to nutrient level ranges, what matters: the actual range or the presence of the nutrients?

For example, blood glucose needs to be in a range around 80-110 or so. It needs to stay in this range. If you had a bloog glucose level of 30, you'd go into hypoglycemic shock and the fact that you still have the presence of glucose doesn't matter: you're toast.

Can a plant absorb nitrate better at a range of 10-15 vs. 1-5? Or is it going to suck up nitrate at the same rate as long as it is present? W ill a plant absorb more phosphate (or absorb it more easily) at 1-2 ppm vs. 0.05-.1 ppm, or is it irrelevant as long as phosphate does not reach zero?

I hope I explained what I meant with that example. I have always wondered this. We never covered anything like this in Botany or Plant Ecology.
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post #15 of 32 (permalink) Old 07-07-2016, 09:30 AM
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Originally Posted by StrungOut View Post
Low tech, low schmeck. Do it in a high light tank, the excel will get the plants no where, where pressurized co2 or diy whichever will.

Correct me if i am wrong.

In a low tech tank there are more variables and room for screw ups. The "excel" eliminated whatever algae is left hence better plant grow.

Do it with high light, excel only see how much you can put in and so on and see where your plants are at.

Thesess are bold statements


Worse week and a bit of my life when I tried it in my tank when the co2 bottle ran out. Under high light I just got bad growth even dosing 6 x normal.
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