# CO2 Injection for beginners



## John Schultz (Jun 21, 2007)

I started a 120L planted aquarium in June and the cycles have just worked themselves out, finally. Algae is pretty much under control. I was sitting in front of the tank last week and noticed that I had not seen any pretty little oxygen bubbles in this tank. I finally realized that maybe with so many plants in the tank and so few fish (only 15 neon tetras) that there was not enough CO2 dissolved to meet the needs of the plants. Moreover, I had been cutting back lighting during the summer. So, I decided to inject CO2. I biked out to the store and got a diffuser, a check valve, a solenoid valve, and started the CO2. I am a brewer so I had regulators and CO2 bottles around so I just used what I had. I started injecting on Oct 9 using a timer to run the CO2 and the light together between 9AM and 6PM. Initially the pH was 5.95. on the 10th it dropped to 5.77 at 8AM. By 18PM the pH had dropped to 5.32. I should have been alarmed at this point but I figured the pH would rise overnight. It did rise to 5.77 at 8AM. But, at about 13PM when I sat down at my desk I found the fish all gasping for breathe at the surface. I rushed to start pumping air into the tank and within an hour the fish were back to the jungle. I got a better regulator and have slowed the CO2 injection. The pH returned to 6.0 on the 13th and 14th. Today I find that the pH has dropped back to 5.7 at 8AM and 5.53 at 18PM. I would expect the pH to return to 5.7 or higher by morning. I would like to ask experienced co2 users what their experiences are with respect to pH cycles and the range of fluctuation they have experienced.


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## gotcheaprice (Sep 4, 2007)

Never used pressurized CO2 yet, but it seems that you don't have a needle valve, so I suggest that for finer tuning after your pH levels have evened out so you can get it right, rather than just raising/lowering your rates all the time.


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## Bert H (Mar 2, 2004)

If you have a drop checker, or can quickly get one, set it up. That's the most accurate way to measure your CO2 levels. If you don't have one, nor can get a hold of one, you need to know the chemistry of your tap water. It's hardness, in particular, to give you an idea of your CO2 levels. From the pH readings you mention, I would bet you have very soft water (low kh).

Most definitely you do need a needle valve for your regulator to finely adjust the gas flow. I would start around 1-2 bubbles per second until you determine your gas levels in the water. Then slowly adjust according to needs.

There will be slight pH fluctuations whether your run your gas 24/7 or use a timed solenoid system. Mine varies +/- 0.2 pH unit with the gas running 24/7. My water is hard which tends to provide a stronger buffering system for the CO2.


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## hoppycalif (Apr 7, 2005)

The pH fluctuations should not harm the fish at all, but the concentration of CO2 in the water that cause the fluctuation can get too high for the fish. Once you go past 30 ppm in the water you are flirting with fish losses. The drop checker, and a needle valve are the way to go - also a bubble counter is good so you have a visible indication of how steadily you are injecting CO2.


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## John Schultz (Jun 21, 2007)

I am not familiar with the drop checker. Is this a kit or device to actually measure CO2 dissolved in the water? I am now using a needle valve and checking the bubble rate from time to time. The water here is extremely soft--30ppm hardness. Basically, the water is snow-melt or rain water that has not had a chance to flow underground. In addition to CO2, I think the water is probably short on mineral nutrients as well. I am going to start doctoring the water this weekend. Welcome any advise.


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## hoppycalif (Apr 7, 2005)

Your homework for the weekend: http://www.aquaticplantcentral.com/...aquarium-projects/32100-diy-drop-checker.html Expect a quiz on Monday!

Some people grow plants in very soft water, and some plants grow much better in that water. But, generally you should add a GH booster such as Seachem Equilibrium when you have water that soft.


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## druda (Oct 19, 2007)

I use CO2 injection for 3 years and I found the rule of thumb that works for me is bubble rate in bubble per minute should be ~ 1/3 of your tank volum in Liters, depending on your diffuser efficiency.In my tanks (GH 7 ,KH 3) it droped from pH 7.0 to 6.7, and there is a lot of O2 comes out.
Udi


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## hoppycalif (Apr 7, 2005)

druda said:


> I use CO2 injection for 3 years and I found the rule of thumb that works for me is bubble rate in bubble per minute should be ~ 1/3 of your tank volum in Liters, depending on your diffuser efficiency.In my tanks (GH 7 ,KH 3) it droped from pH 7.0 to 6.7, and there is a lot of O2 comes out.
> Udi


That "rule of thumb" isn't of much value. If you have a good surface current you will lose CO2 and need more bubbles per second to make up for it. If you use a good external reactor, where 100% of the CO2 is dissolved into the water, you need less bubbles per second. There is no method for determining that you have a specific amount of CO2 in the water that works at all accurately other than the drop checker method.

It is also becoming more and more apparent that good water circulation in the tank is at least as important as having a specific amount of CO2 in the water. The more heavily the tank is planted the more important water circulation becomes, and the less likely that we already have it.


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## Uncle Rico (Oct 22, 2007)

Is it important to be able to measure the actual amount of CO2 in the water, or is measuring the rate of CO2 injected in the water via a bubble counter good enough?


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## Squawkbert (Jan 3, 2007)

It is all important - Ideally, you know that you have good circulation, slight rippling at the surface and a nice green drop checker. If all is well, one component can fail withour endangering your tank's fauna. If things are out of balance, you end up having to pump in lots of CO2 to maintain a decent level for plants. In this situation, a powerhead or pump failure results in CO2 poisoning of the fauna, not to mention having to spend more $ on CO2 than you should need to.


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