Is it possible to over-dose with CO2 a 15 gallon tank if I use a 2L pop bottle? Would it be better if I were to use a 1L or a 500ml bottle?
The inhabitants are 15 CPD's, 2 Pygmy catfish and 5 Amano shrimp...not counting the hundreds of snails that I don't care about. The PH is low...in the range of 6.0 and it is a room temp tank...typically around 68 - 70 degrees.
It's rare, but I made it happen ... ;) ... when the initially production of CO2 peaked due to increasing bacteria populations and low alcohol content. Another contributing factor here is temperature. That tank was quite warm, maybe close to 80, and the CO2 bottle squeezed right behind it. So it had a similar high temperature and made the yeast go crazy.
Rather than reducing the volume of the bottle, I lowered the amount of yeast and sugar, so that this initial peak was much lower. It also produces CO2 for a longer period of time. But with your temperatures you are probably ok without doing too much tweaking.
One important thing to remember when starting CO2 for the first time on the tank: be around and keep any eye on your fish every once in a while. And keep in mind that DIY CO2 also runs at night.
Right...I can't exactly shut it off can I?
Hmmm...
Is that normally an issue?
You can't shut it off easily. In most cases, it's not a problem. Just keep an eye on it.
You can't shut off the flow of gas easily. But if your method of dispersal is based on a powerhead or a Mini Elite filter, that device could be run on a timer. This is rarely necessary though.