DIY CO2 control - The Planted Tank Forum
 
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post #1 of 10 (permalink) Old 09-18-2011, 12:36 AM Thread Starter
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DIY CO2 control

I've been adding a small 9 gal shrimp tank to my collection. However, to keep the nitrates down the plants I've put in the tank need some help.
Today I started up some DIY co2 and it's been going strong. One if the plants in the tank even started bubbling a little. Now its night and from my measurements there is approximately 15 to 16 ppm of co2. I know the story about how the tests and chart are unreliable but fir me so far they've worked great. I have really soft water here 18 ppm kh (and ph now of 6.2 .... lower than I kind of want but it'll work for now).
Anyway this all brings me to my question, using the DIY method (fermenting sugar water with a hose going to an airstone) is there a danger of putting too much co2? Especially at night when the plants won't be using it up?
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post #2 of 10 (permalink) Old 09-18-2011, 12:55 AM
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if you are worried about it at night, you can either increase surface agitation by either increasing the filter rates if you can....or by adding an airstone at night on a timer....for my 36 gal I use an airstone, but I use pressurized co2....I run the airstone 1-1.5 hrs after lights go down until about 30 min-1hr before the lights come back on to allow co2 buildup....works like a charm for me....you may also want to add a bit of crushed coral....I use a tiny amount in a nylon baggie....helps to raise KH and GH which also increases the ph....but the CO2 helps to lower the ph and keep things in check.....plus the higher GH would be beneficial for your shrimp
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post #3 of 10 (permalink) Old 09-18-2011, 12:58 AM
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I also have very low KH in my tap water, so I need the coral to help allow for better buffering of my pH....some say baking soda works....but I like my method better....Also, shrimp are fairly sensitive to CO2 from what I know, so I would be a tad leary of it during the night
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post #4 of 10 (permalink) Old 09-18-2011, 02:54 AM Thread Starter
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I've decided to buffer my water.. it's a bit soft and I want to breed them.. from what I've read they like harder water (cherry shrimp do at least).. and higher pH (mine out of the tap is good at around 7.2 but too soft) .. I'll add some air bubbles at night to keep the co2 from going up too much.

I'm finding I'm a control freak and don't like that I can't control this better.. I like the ph controller solenoid solution.. it's nice
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post #5 of 10 (permalink) Old 09-18-2011, 08:35 PM
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I've heard some horror stories about water changing hardness and having pH controllers gas fish too. I'm a bit of a control freak as well, but this has been good so far in getting me to ease up.
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post #6 of 10 (permalink) Old 09-24-2011, 01:15 AM Thread Starter
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I broke down and bought a needle valve and bubble counter
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post #7 of 10 (permalink) Old 09-24-2011, 01:54 AM
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You can't safely use a needle valve unless you've got a bottle active as a reservoir that also contains a pressure relief valve. Otherwise, you're looking at a mess on your hands.
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post #8 of 10 (permalink) Old 09-24-2011, 02:20 AM
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You can turn off the DIY CO2 by putting a tee, with a check valve downstream of it, and a little shutoff valve on the side of the tee. Open that shutoff valve and nearly all of the CO2 is dumped before it gets to the tank. Close it and the CO2 has to go to the tank again. You could do that manually every night, or use a solenoid valve to do it for you with a timer.

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post #9 of 10 (permalink) Old 09-25-2011, 01:56 PM
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That's a good method, Hoppy. The OP just needs to know that it can take several hours to rebuild the lost CO2 from an open valve.

If they spend a few more minutes and maybe $8-$10, they can put a manifold on a cap and install a pressure relief valve. There are a few threads here on the forum that discuss it.

Standard 2L Coke bottles handle somewhere north of 90psi without a problem. I've got 75psi relief valves on my reservoir bottles and have never had them go off. But I've never had to waste CO2 or wait for pressure to build back up, either.
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post #10 of 10 (permalink) Old 09-25-2011, 03:20 PM
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Another way to achieve some control of DIY CO2 is to use a powerhead to diffuse the CO2, by chopping the bubbles into very fine bubbles, which dissolve CO2 in the water much better. Turn off the powerhead and most of the CO2 goes to the water surface in big bubbles. With this method you have to be very careful to be sure the powerhead doesn't create suction on the CO2 line, which could suck the contents of the CO2 generator into the tank.

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