DIY CO2 setup finally

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evercl92

Aquarium Advice FINatic
Joined
Jul 7, 2006
Messages
643
Location
Groveport, OH
I finally got around to setting up a simple DIY CO2 system. I put the following recipe in a 2L bottle, last evening:

4 cups sugar
4 cups water
1 1/4 tsp bakers yeast
1 tsp baking soda

The problem that I've come across is that it's not producing CO2 like I would have expected. I have the bottle on the ground, air tubing has to run vertically 4-5 feet, then 2 feet to the bottom of the tank. I am currenly using a simple air diffuser (awaiting arrival of a glass micro-bubbler). I've seen a couple bubbles since yesterday, but definatly not a constant flow. If I squeeze the bottle, bubbles come out the diffuser. I have a check valve at the peak of the tubing, where it enters the tank.

I'm looking for insight to why I haven't seen higher CO2 production?
I dont find any leaks in the tubing or elsewhere.
Wrong recipe? Didn't wait long enough? Too high of pressure to overcome to force the flow into the tank?

As always, TIA
 
I can see several potential problems.

1. Too much Sugar. You should only need about half that amount.
2. Too much Yeast. You should only need 1/4 tsp.
3. Bakin Soda. If your water is already pretty hard this can kill or severely depress CO2 production. Next time try halving or eliminating it altogether.
4. Bottle location and length of tubing. A lot more pressure will be need to overcome these issues. With your other possible problems it may be too much for the mix to overcome.
 
i second that u are using too much sugar and too much yeast. a good recipe that i use is as follows:
2 cups of sugar:put suar in a bow or measuring cup and cover with boiling water. mix till sugar is completly dissolved and add to bottle then add cold water to make it luke.
1/2 table spoon of yeast: i find this produces faster but not for as long which is what i prefer casue u get higher levels. mix it in some luke warm water till mostly dissolved(a few min) then add it to the bottle with sugar. fill the rest with tepid water up to the beginning of the neck with water and u are done. u will see production within 15-20 min. make sure u shake the mixture to get the sugarwater and yeast going.

that is justa simple reciepe that has worked for me but there are many many others out there to try.
 
I'm not sure about the mix but I used a similar recipe to mr funktastic. It worked well.

My problem was, that I was losing some pressure from my airline to soda cap connection. When I reconstructed that spot it worked perfectly. You might want to double check all your potential pressure losing spots.

Oh yeah, it took me a while to figure out because it seemed to work if I squeezed the bottle. :wink:
 
awaiting arrival of a glass micro-bubbler

You may find your DIY CO2 does not have enough pressure to push through some glass/ceramic diffusers. Even worse, somthing else may fail before building enough pressure to bubble.
 
I agree with the others on the recipe. I use 6 cups of water, 1/4 tsp of yeast and 1/4 tsp or baking soda in a 2-liter. I "melt" my sugar in with hot water before adding yeast/baking soda.

I would double check a few other things:

-- make sure your air lines are sealed properly (no leaks at the bottle top)
-- check the diffuser by just leaving the airline open in the tank and see if anything comes out

My bottles are the same distance from the tank as yours, so I don't think distance is a problem. Make sure you are using CO2 compliant tubing or at least use silicone tubing over regular rubber airlines.
 
Thanks for all the info. I did find a small leak at the top of the cap, where the tube goes through it. I had previously sealed it and I dont recall it leaking. I resealed it in the meantime. So, sounds like I need to use:
2 cups sugar
4-6 cups of water
1/4 - 1/2 tsp yeast
1/4 tsp baking soda

My tap water has a gh of about 12, kh 1.
Do I need to add the baking soda then?
Is it necessary to use CO2 approved tubing since it's not a pressurized system? Currently I'm using standard airline tubing.
 
the standard airline tubing will just dry out faster an deteriorate casue u to loose some co2. fine for a shorter period of time though. your water seems to be hard enough that u dont need to add the baking soda. if it seems to burn out quick though once u redo the mixturee try adding a very small amount of the baking soda to lengthen the batch.
 
I only said that cuz I read somewhere that regular air tubing actually loses the CO2 through the walls ... I am only regurgitating what I read elsewhere. The silicone tubing still loses some but is much more efficient. I use the silicone since I couldn't find any co2 rated tubing in my local stores and I didn't feel like paying for shipping from onliine stores.

I would play around with the different amounts in the recipe to see what works best in your water. Try it with and without the baking soda to see which works better for your water. Try a little more or a little less yeast as well. If you start with the formulas that everyone else is sharing, you'll have a good starting place.
 
I set up a new mixture, totally dissolved the sugar. I tried a new recipe:

2 cups sugar
5 cups water
1/2 tsp yeast

I see CO2 production at the surface of the water (foaming bubbles and such), yet I still dont see any production at the diffuser. Redid the seals at the at the bottle cap, with aquarium sealant, both inside and out. I only have the diffuser down in the water about a foot, not even at the bottom of the tank. My only real guesses are: 1) that the tubing is too long, 2) the diffuser is too restrictive, 3) the bottle being on the floor is too much for the simple pressure to overcome the the 5 foot vertical climb then 12 inches into the water.

I might have to change some tube lenghts, put the bottle on the top of the tank, and such.
Other ideas or confirmation of my guesses appreciated.
 
I would try it without the diffuser to check. I don't think the length of tube or it being on the floor are the problem. As you said, maybe the diffuser is too restrictive.

Just a thought though. I think the sealant I used had to dry overnight. Are you sure it's dry and sealed well?
 
you can try moving the bottle on top of your light/hood ... in the past, I was able to get better production that way ... but my theory is that it is more a result due to the heat from my light rather than the height or distance (I kept the same long tubing ... so distance is out)
 
The air in the CO2 line has a very low density compared to water. Raising or lowering the bottle 3 or 4 feet should have a negligible effect. In other words, it won't make a difference.

See if the bottle feels tight to the touch. That's how I can tell if I'm producing.
 
I redid the cap and seal this morning. Drilled a slightly smaller hole, so the tube fits tighter. I used liquid nail to seal the outside of the cap. The bottle did feel tightish before I replaced the cap. I assume you guys all use check valves as well? Surely it's not hindered by a check valve? I also removed the diffuser piece. I'll check it in an hour or so.
 
Check valves are highly recommended and will only cause problems if they are installed backwards.
 
what kind of diffuser are u using? i agree that the height and length of the tubing has no effect. another thing that i find really really helps is to scratch the plastic cap with a sharp knife or something anywhere that the silicone is going to touch it. this will give the silicone somewhere to grab hold rather than a smooth suface, should make a better seal. u can watch the co2 moving down the airline in the water. once u see it start moving down the line shake the bottle a little. this will casue a burst in production and u will be able to see if the bubble can move through your diffuser. if they still do not go through i am going to assume that your diffuser is made for a pressurized set up. i dont use a check valve but do have a drip loop in my set up to avoid water being transfered.
 
not the exact brand and all, otherwise the same
air_pumps_lees_discard_a_stone.jpg


I have removed it though. I see a bubble or two now and then (maybe an hour or so), nothing constant.

When I redid the cap, I took 80 grit sandpaper to the top of the cap, roughed it up a bit.
 
there is a leak somewhere then.there is no way that it is only producing a bubble or 2 every our.are there any connectors besides the caps? i know that i have 2 bottles connected by a T-splitter and i had a problem with it when i first set it up.
 
I have, in this order: 2L bottle, cap/tubing sealed with liquid nail, tubing goes 5 feet, check valve, another 2 feet of tubing. The tubing, bottle, check valve are all new. I guess I'll cehck it all again..

Ok, I was out of town for a day and a half. So, before I left, I redid the seal on the cap, again. Used liquid nail again, and it will have sat drying for 36 hrs before I get a chance to set it back up (tomorrow morning). Hopefully this will correct the issues.
 
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