need some CO2 tips - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 21 Old 12-10-2007, 06:20 PM Thread Starter
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need some CO2 tips

well, I might have to bite the bullet and get some cO2 for my tank. Probably DIY CO2 because I am very frugal. I need some tips from people who have done this before.

A) How can I ensure that my bottle will not blow up?

B) How can I ensure that the yeast/sugar won't get sucked into my aquarium?

C) What is the smallest, easiest-to-hide-the-equipment way to diffuse CO2 in my tank? my tank is very small, 15 gallons ... i don't want to put any more "things" inside the tank if I can avoid it...or if i do they must be very small and easy to hide...

thanks in advance!
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post #2 of 21 Old 12-13-2007, 02:09 AM
PM fish4all. He is the resident CO2 guru.
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post #3 of 21 Old 12-13-2007, 12:26 PM
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DIY is rather easy, the only real hard part is to get the whole thing to stay sealed with no leaks.

2, 2 liter bottles sealed with thread tape, the white tape for preventing leaks, with a catch bottle in the middle. I have a drawing somewhere but if I can't find it I will make another one today I hope.

As for a diffusor, what type of filter do you have? If you have a good HOB then you can pipe the CO2 directly into the intake and the filter will do a majority of the diffusion for you. If not, we will work on something else that is small and easy to use.
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post #4 of 21 Old 12-13-2007, 05:14 PM Thread Starter
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I have a Whisper hang-on-the-back filter ... but I was thinking about getting a different filter someday soon because this one makes a lot of surface movement.

what is the catch bottle for?
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post #5 of 21 Old 12-13-2007, 06:19 PM
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one bubble counter. also if the co2 goes out there is a chance water flows back in the line.

2 liter bottle shouldnt blow up. mythbusters inflated one to i think 80+ psi.

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post #6 of 21 Old 12-13-2007, 07:44 PM
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The catch bottle is just that, it is inline from the 2 liter bottles to catch any overflow you might have from the bottles. I used a small peanut butter jar, a plastic one for this when I did mine. I fed the CO2 right into the intake of my AC filters and could get levels up to 50ppm.

As for the bottles exploding, always check to make sure they are not clogged. I have seen pictures of the aftermath from DIY CO2 exploding and it was a nasty mess. That and the smell is not the most pleasant if you can imagine a straight alcohol and yeast mixture all over the room.

Check valves are also recommended by some but I could never get them to work for me.

I will have the picture when I have time and feel up to drawing one if I can't find the ones I have already. Sometimes I hate computers, can never remember where I saved something.

And don't worry about CO2 displacing oxygen, it simply doesn't happen. Fish gasp at the surface because levels get too high, not because of the lack of oxygen. Levels should stay between 30 and 50ppm. Also, make sure your KH is at least 3dKH to prevent major pH swings and stays there. CO2 will lower you pH and a low or non existant KH can cause serious trama to your fish from pH swings.

Download the following calculator to help you keep track of your CO2 levels as well as guidelines for dosing fertilizers.
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post #7 of 21 Old 12-14-2007, 12:57 PM
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Crude I know but it gives the idea.
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post #8 of 21 Old 12-15-2007, 03:01 PM Thread Starter
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Thanks for the tips and the picture!! would I put the sugar/yeast mixture in both of the bottles on the left? And why 2 bottles, is that to produce more CO2? why is the longer airhose stem needed in the catch bottle?

also this might be a dumb question but is it OK for the bottles to be lower than the tank? I would have to hide them somewhere on the floor because the back of my tank doesn't have any background on it ... it's open so that it can get some window light. i have a hard time hiding my wires and stuff because of that, but the plants seem to like it a lot.
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post #9 of 21 Old 12-15-2007, 04:46 PM
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2 bottles serve 2 purposes. The first you pointed out, more production. The other purpose is so that you can rotate out bottles instead of making new mixes in both bottles at the same time. As you can imagine, this will allow for consistant levels and less of a drop off when replacing bottles.

The longer tube allows for anything that might get into the bottle to be out of the reach of the shorter tube. That way if you do have any overflow, I never saw any, there is very little chance of any of it fouling your tank.

As for putting it below the tank, yes you can but you will need to use check valves for sure to prevent reverse suction from ever occuring. Make sure not to skimp on the quality of the check valves either as the alcohol mixture and the CO2 are hard on them and cause the cheaper ones to fail quickly.

There is a plumbing fixture called a bulkhead that can make the whole setup much easier to use. They are spendy at $5-7 for a pair but for the ease they would create in changing bottles it would be worth it. If I ever do another DIY setup I will use them for sure.

Also, if you put quality check valves on the tubing for each bottle and on the main feed to the tank you can change out a bottle without interupting the flow of CO2 from the other bottle. It may slow it down but it shouldn't stop that way.
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post #10 of 21 Old 12-15-2007, 05:03 PM
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That is one of the best sites I have found for DIY CO2.
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