Okay so I built my first DIY CO2 reactor. It was probably the easiest thing to make. Here's the instructions for anyone who wants to make one.

Things you need:
-Sauce bottle like the ones at restuarants.
-Airline tubing.
-Soda bottle.
-Pump or powerhead.
-Activated yeast.

Steps:
1.) Obtain an old water or soda bottle. Preferably a small one.
2.) Cut the bottle where the neck merges into the rest of the bottle and becomes the full size. Throw the rest away.
3.) Cut a hole the size of the airline tube in the cap of the bottle and one in the side, about mid way down.
4.) Cut the airline tube to the required length for your setup.
5.) Install the two seperate airline tubes, one in the top (for the pump or powerhead) and the other in the side (for the CO2). You don't need to seal them but you can if you would like.
6.) Put the airline tube coming from the side of the bottle onto the top of your sauce bottle.
7.) Place the other tube coming from the cap of the bottle onto your powerhead or pump.
8.) Boil a small amount of water to fill the bottom half of the sauce bottle. Mix in 5 cups of sugar when it starts to boil. Let it sit until cool or lukewarm.
9.) Activate the yeast! Pour a spoon full into a mix of lukewarm water and sugar. Just enough to fill the other half of the bottle.
10.) Once the yeast has started to bubble and the boiling sugar mix is lukewarm mix the two together into the sauce bottle.
11.) Cap the sauce bottle and place your diffuser in your tank wherever you desire.

You can also put a mesh cover over the bottom of the bottle to let out only tiny bubble, but I find it works fine either way. Hope you enjoy and can use this.

That seems a lot harder than what I did.

I took a plastic gallon water container and poked a hole in the lid where I stuck the air line. The air line went directly to the intake for my Rena canister filter(I actually made a hole in the priming cap) and siliconed both air line/cap conections.

I just got warm water from the tap, filled the gallon jug 2/3rds the way full and added the 4-6 cups sugar and a teaspoon of yeast and shook it for a bit, and then hooked it up.

The canister filter workes great as a diffuser, and if no pH buffers are used, you can measure the co2 level by the KH level and the pH through an easy formula.

The only problem I had was that the co2 seemed to disintigrate the plastic water jug lids and they would need remaking after a couple of weeks. I'm going to try a different lid next time.

Remember that at night the plants will put out co2 and not o2 so it's good to run a powerhead/venturi at night so the fish don't get poisoned and suffocated.

PK i run 2 filters on my 55 gal planted 1 canister and one HOB what if i were to do what you did but hook it to the intake of my HOB filter and put the HOB on a timer? think that would work. And how did you figure how much Co2 to put into your tank, how much water to suga to yeast to mix. i read about bubble counters and all that and if you do it the way you are describing how do you "count the bubbles"

The whole idea with using a canister instead of a hob is because the co2 is trapped within the canister for a while and I don't think a hob would even work as a diffuser.

The reason I don't just disconnect the co2 during the night is because there is a huge pH swing from like close ot 6.0 to like almost 8.0 without the co2 and I thought it would be better to leave it on and just up the aeraton at night. This would take care of the o2 drop at night as well as the co2 spike.

I actually took the air tube that goes from the jug to the filter and I put a loop in it where I let some water sit. It acts like a bubble counter, sort of, as you will be able to see if it's going faster or slower than a figured out rate for a certian ppm co2. I believe 30ppm is the amount you're looking for.

I played around with different amounts of yeast and came back to a smaller amount than a larger, as it lasts like a week instead of a day. I used about a teaspoon yeast to roughly 5-6 plus/minus cups of sugar. Oh, and the solution ended up filling the container about 3/4ths full.


I had a big problem once when the sponge filter fell off the canister intake. A big snail plugged up the intake and all the suction went into the co2 container sucking it all into the fishtank. I had a nasty ass tank for a while, so make sure that doesn't happen.

well im making a canister filter how does that work?

I'd run the co2 line right into the intake tube(by making a hole in the tube). Have a loop that would be like a "drip loop" for a power cord in the co2 line and put a little water in there. The co2 bubbles out slow enough that it will act like a bubble counter of sorts.