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Discussion Starter · #1 · (Edited)
For many years it has been believed that the ideal level of CO2 in a planted aquarium is about 30 ppm or even more. Because of this it is widely believed that DIY CO2 use is limited to small tanks, like 10-20 gallon tanks. But, several years ago the scientists at Tropica published a paper with some data in it that clearly shows that CO2 levels at much less than 20 ppm is very beneficial to the plants when you use less than high light. See: http://www.bio-web.dk/ole_pedersen/pdf/Hydrobiologia_2202_477_163.pdf Our atmosphere contains about 400 ppm of CO2, and when water is exposed to that CO2 we get around 3 ppm of CO2 in the water. Even without the CO2 that comes from our substrate due to normal decay of organic matter, we always have around 3 ppm of CO2, so if we add another 3 ppm of CO2 to the water we have doubled the CO2 available to our plants.

You can use the data in that paper to show how effective low levels of added CO2 can be. The data, in a different form is:



If you graph this data you get:



Note that doubling the ppm of CO2 from 3 to about 6 ppm triples the growth rate at very low light - 25 PAR - and an even smaller increase in CO2 results is as high a growth rate as you can get with that much light. Clearly there is a lot to be gained with non-high light tanks using the relatively small concentrations of CO2 that you can get with DIY CO2.

Re-graphing that data:



This shows that even for medium light a small increase in CO2 is very effective. You get as much improvement with as little as 10 ppm of CO2 as you do with much higher CO2 levels. This encouraged me to start using DIY CO2 on my 65 gallon tank.
 

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Indeed. I pump it into my low light 20l using the citric acid and baking soda with good results. I know you had trouble with that method Hoppy but I'm still a believer.

Sent from my XT1585 using Tapatalk
 

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Discussion Starter · #3 · (Edited)
When using CO2 at levels below 20 ppm you can't use a drop checker with 4 dKH water in it to measure the amount of CO2 you have. The color stays too blue to be able to use it. But, if you dilute the 4 dKH water 50-50 with distilled water you have 2 dKH water, and that water will change to green at about 15 ppm. I diluted it to 1 dKH for my drop checker, and I shoot for yellow instead of green. I find this easier for my eyes to judge the color. When you use different KH water in the drop checker, this is the effect of doing that:

 

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Discussion Starter · #4 ·
I diffuse my CO2 using a Hagen Elite mini filter. This is a very tiny internal filter, which you can use without filter media, poking the CO2 tube into the little filter chamber, so the bubbles go through the tiny pump, getting chopped into microbubbles. To avoid any back flow of water to the CO2 generator bottles I put a small, very resistant to chemicals check valve on the end of the CO2 line, and poke the outlet into the filter chamber.



I purchased these from US Plastics website.

The result is pulses of CO2 bubbles sprayed into the tank water. The bubbles are so small they spread out throughout the tank. And, my drop checker stays yellow-green to yellow 24/7. That isn't enough to harm the fish at all, so running it continuously works fine. I'm using 2 two liter soft drink bottles in parallel, so I can change one bottle every week and keep a relatively steady level of CO2.

To avoid BBA attacks I also dose Metricide 14 at 1 ml per 10 gallons of water daily. This has been the most successful planted aquarium set-up I have ever had.
 

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Discussion Starter · #5 ·
Indeed. I pump it into my low light 20l using the citric acid and baking soda with good results. I know you had trouble with that method Hoppy but I'm still a believer.

Sent from my XT1585 using Tapatalk
If you can get the citric acid/soda method to work I agree that it is a better method, but I just couldn't make it work. I'm happy with the yeast/sugar method, so I don't even try my citric acid method anymore.
 

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Discussion Starter · #6 ·
There are several designs of drop checkers, all of which will work, but I find this one to be the easiest to use, because of the white background that lets you see the color accurately, and the shape of the fluid chamber, which lets you use a small enough amount of fluid so it reacts to changes in a reasonable time.



I bought this on EBay, but they are available from other stores too.
 

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Subscribed to a great thread. Will you add your CO2 recipe and water change schedule here so it is one stop shopping for a summary of your most successful aquarium with regards to carbon?

With daily Excel dosing, do you find anything goes awry if you miss a weekend or go on a weeklong vacation? Do algae take advantage of this short term parameter change?
 

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Discussion Starter · #9 · (Edited)
My CO2 recipe is: About 1 tsp of bicarbonate of soda, 1/2 tsp of baking machine yeast, 2 cups or a little less of granulated white sugar. I add those to a 2 liter bottle, fill it to just past the start of the neck with just warm water. Then I use my thumb to "cork" the bottle and shake it up good to avoid undissolved stuff in the bottom. Then screw it onto the cap, which has a check valve on it, so no CO2 is lost during the change. Every week plus or minus a day or two, I change a bottle, alternating bottles.

Once a week, on average, I do my pruning, clean the glass all around, and drain about 50% of the water and refill with cool tap water, adding Prime at the beginning of the new water addition. If I'm busy when water change day arrives I test the nitrates - 40 ppm means change water, 20 ppm means I can skip a change.

I don't go away on weekends, other than for one day occasionally, so I follow my routine of fertilizing and feeding every day. I fertilize with about 1/4 to 1/2 of the EI dosage schedule for a 50 gallon tank, cutting the KNO3 dose in half and substituting K2SO4 for the other half. I dose every day, alternating between CSM+B and macro elements. And, every day I dose about 5 ml of Metricide (equal to almost twice that of Excel).

My Planted Plus 36 inch light sits right on top of the tank. It is on for 8 hours a day.
 

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Quite informative Hoppy, thanks a lot.

Right now i drop small doses of Seachem Acid buffer & Alkaline buffer, daily, in my Excel tank to generate some co2. Acid buffer "eats" the KH and produce co2.

Michel.
 

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Discussion Starter · #11 ·
I don't think it does any good at all to supply small surges of CO2 once a day. Plants need time to adapt to using the level of CO2 they experience. A surge, which is quickly dissipated at the water surface doesn't give them that time. The best CO2 is a concentration in the water that stays the same throughout the photoperiod, and is at the same concentration every day. The closer you get to that, the more effective the CO2 is.
 

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When using CO2 at levels below 20 ppm you can't use a drop checker with 4 dKH water in it to measure the amount of CO2 you have. The color stays too blue to be able to use it. But, if you dilute the 4 dKH water 50-50 with distilled water you have 2 dKH water, and that water will change to green at about 15 ppm. I diluted it to 1 dKH for my drop checker, and I shoot for yellow instead of green.
Great information on CO2. I am diluting my 4 dKH water into 0.5 and 1 dKH water. Do I have to store them in opaque bottles. I only occasionally take them out from cabinet to bright indoor light for testing.

I have no plan to inject CO2 yet, but want to test the baseline CO2 fluctuation during and between photo periods. I will dose Excel / Metricide and want to see if it has any effect on CO2.

Our atmosphere contains about 400 ppm of CO2, and when water is exposed to that CO2 we get around 3 ppm of CO2 in the water. Even without the CO2 that comes from our substrate due to normal decay of organic matter, we always have around 3 ppm of CO2, so if we add another 3 ppm of CO2 to the water we have doubled the CO2 available to our plants.
I think the above figures are misleading. ppm is parts per million by weight. Since air weighs a lot less than water, 400 ppm in air is not 100 times greater than 3 ppm in water. There is formula that converts ppm by weight to ppm by volume so the comparison can be made on the same ground.
 

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Discussion Starter · #14 ·
Great information on CO2. I am diluting my 4 dKH water into 0.5 and 1 dKH water. Do I have to store them in opaque bottles. I only occasionally take them out from cabinet to bright indoor light for testing.
No need to keep them dark. The water is almost pure water.
I have no plan to inject CO2 yet, but want to test the baseline CO2 fluctuation during and between photo periods. I will dose Excel / Metricide and want to see if it has any effect on CO2.

I think the above figures are misleading. ppm is parts per million by weight. Since air weighs a lot less than water, 400 ppm in air is not 100 times greater than 3 ppm in water. There is formula that converts ppm by weight to ppm by volume so the comparison can be made on the same ground.
When measuring ppm of constituents of atmospheric air, I'm pretty sure the numbers are in ppm by volume, not weight. But, when measuring ppm of substances dissolved in water, the numbers are ppm by mass. So, 400 ppm of CO2 in air is by volume, but 3 ppm of CO2 in water is by mass. The two concentrations are related, but not without correcting them to be on the same basis. We do get about 3 ppm of CO2, by mass, in water from the atmosphere, which is 400 ppm of CO2 by volume.
 

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No need to keep them dark. The water is almost pure water.

When measuring ppm of constituents of atmospheric air, I'm pretty sure the numbers are in ppm by volume, not weight. But, when measuring ppm of substances dissolved in water, the numbers are ppm by mass. So, 400 ppm of CO2 in air is by volume, but 3 ppm of CO2 in water is by mass. The two concentrations are related, but not without correcting them to be on the same basis. We do get about 3 ppm of CO2, by mass, in water from the atmosphere, which is 400 ppm of CO2 by volume.
Here is how ppm by volume is converted to mg per m3 in air.

http://www.lenntech.com/calculators/ppm/converter-parts-per-million.htm

Accordingly, 400 ppm of CO2 in air by volume is equivalent to 775 mg/m3 or 0.775 mg/l in air by weight. So saturated CO2 in water, 3 mg/l, is actually higher than CO2 in air. So CO2 limitation in water is really a diffusion / transfer limitation
 

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Discussion Starter · #16 ·
Here is how ppm by volume is converted to mg per m3 in air.

http://www.lenntech.com/calculators/ppm/converter-parts-per-million.htm

Accordingly, 400 ppm of CO2 in air by volume is equivalent to 775 mg/m3 or 0.775 mg/l in air by weight. So saturated CO2 in water, 3 mg/l, is actually higher than CO2 in air. So CO2 limitation in water is really a diffusion / transfer limitation
Parts per million by volume is ml/1000 liter, not mg/l, isn't it? If you separated out the CO2 in air into a balloon you would get a 400 ml volume balloon of CO2 from a one thousand liter balloon of air.

When I try to convert between these two methods of measuring ppm I always end up totally confused:rolleyes:
 

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Parts per million by volume is ml/1000 liter, not mg/l, isn't it? If you separated out the CO2 in air into a balloon you would get a 400 ml volume balloon of CO2 from a one thousand liter balloon of air.

When I try to convert between these two methods of measuring ppm I always end up totally confused:rolleyes:
Yes, ml/1000 liter is ppm by volume, which is only used for air measurement. It makes no sense to express any gas or solute in ppm by volume in water because of ionization.

mg/l is nearly the same as ppm by weight in water because 1 liter of water weighs 1,000,000 mg. But in air, the conversion is complex. CO2 can also be expressed in mg/l in air by weight, but mg/m3 is conventionally used. 1 m3= 1000 liter so 775 mg/m3 = 0.775 mg/l
 

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Every day I dose about 5 ml of Metricide (equal to almost twice that of Excel).
Is the Metricide 2.5% Glutaraldehyde and are you dosing it at this strength?

i found that you answered my question in another post."Has SeaChem Excel changed the formula"

I can't answer the question, but I do dose Metricide 14 the same as Excel, 1 ml per 10 gallons of water. I dose it daily, 5 ml in about 50+ gallons of water in my 65 gallon tank. It is working great for me. I use it to avoid BBA attacks which my DIY CO2 would lead to as the concentration of CO2 in the water varies from day to day.

Most people mix Metricide with water to reduce the concentration to 1.5%, but I have never seen any reason to do so.
 

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Discussion Starter · #19 ·
I diffuse my CO2 using a Hagen Elite mini filter. This is a very tiny internal filter, which you can use without filter media, poking the CO2 tube into the little filter chamber, so the bubbles go through the tiny pump, getting chopped into microbubbles. To avoid any back flow of water to the CO2 generator bottles I put a small, very resistant to chemicals check valve on the end of the CO2 line, and poke the outlet into the filter chamber.
My little Hagen Elite mini filter quit working, for no reason I could find. So, I bought a really small submersible water pump from Amazon, and substituted it.



That little pump looks like the same one used in the Hagen Elite, but without the filter chamber. It works as well as the Hagen filter. And, it is really cheap! About $8, as I recall.
 
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