Question About DIY CO2 "Filter"

[raulfd4]

I have been looking online at different DIY CO2 setups. They are all pretty similar. However, I keep finding one discrepancy. In some diagrams, they set up the "CO2 Filter" filled with water, and others just have an empty bottle.

Which one is right? If you look at my diagram, my question is:

Should container "B" filter the CO2 gas using water, or should that bottle just be empty - possibly catching any yeasty water that may come through the tubing?

It just seems like if I use water, much of the CO2 will be released into that water (even though there isn't a diffuser) and won't make it into the aquarium.

[Cliff]

actaully, I think both are right. I have tried both and didn't see a difference. I don't use any water now, just a empty container to help prevent the mixture from getting into the tank

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[Piscine]

I don't use the filter and haven't had any problems (yet).

[dbosman]

Bottle B should have water in it. Not as much as the illustration shows though. The long tube should reach the bottom or just off the bottom. The short tube need only be long enough to keep the seal at the top of the bottle. The reason for water in your filter bottle is to trap any gunk that might bubble out of the yeast bottle or bottles. CO2 will be captured by the water in the filter bottle, but it will only be captured once and only to saturation. After that all the CO2 generated will go to the aquarium.
An empty filter bottle is just an emergency over flow for yeast gunk.
The problem is some gunk that bubbles out of a yeast bottle into an empty bottle *may* get into your tank. With a clear filter bottle and water for the gunk to mix in, you'll see any trouble before it gets to your tank.

I may have missed it, but a check valve will keep aquarium water from back siphoning if you get a leak in your CO2 system.

Daisy chaining yeast bottles is a good idea by the way. If you have multiple bottles (I like three) you can always have a fresh lively unit and one that is exhausting. DIY yeast CO2 typically lasts for three weeks, so if you have three bottles, you just do one fresh one each weekend.

Oh, yeah. One last bit. Secure the bottles in an upright position. A yeast generator spilling onto a significant other's carpet might lose you an aquarium.

[raulfd4]

Thanks folks. Although this doesn't have much to do with the original post, I figure I might as well ask while I have some sort of audience. I am planning on using a 1 liter bottle for my yeast mixture. Is this enough for my 20 gallon? Should I just use a 2 liter? I don't want to overdo it, but from what I've seen, it seems like that is hard to do.

[Aeonflame]

Is your tank heavily planted? if so, go for the 2 liter bottle.

[dbosman]

Thanks folks. Although this doesn't have much to do with the original post, I figure I might as well ask while I have some sort of audience. I am planning on using a 1 liter bottle for my yeast mixture. Is this enough for my 20 gallon? Should I just use a 2 liter? I don't want to overdo it, but from what I've seen, it seems like that is hard to do.

Start small and work up if you wish or find it useful for you. The bottle cap is the same size. It's not impossible to over do DIY CO2. The biggest problem is the yeast reactor runs 24/7 so during he night when the plants can't use it, CO2 is still bubbling into the tank. Your pH may drop lower than you'd want. The simple solution is an air stone. That will create surface agitation and help dissipate the CO2. Turn it off during the day so CO2 will stay in saturation for the plants.

[funkman262]

Great explanation by dbosman about the purpose of water in bottle B. One more thing to add though is that by having water in there, you can actually see the bubbles so you can use that catch bottle as a bubble counter. I check that bottle from time to time to see how quickly it's bubbling to figure out if it needs to be changed or not.

[raulfd4]

Right now I am just going to start out with some java fern and anubias nana. So, no, it won't be that heavily planted. I did buy an airstone in order to make sure that I could run it at night to avoid a pH crash. I will be putting water in the filter bottle to use as a bubble counter. I didn't even think of that. Thanks again for all of your help!