Planted Tank Guru
Join Date: Sep 2006
Location: Northern California
Use #1 with the following changes: Have the bubbler go one right when the lights go out. CO2 outgasses very quickly.
2 or 3 sponge filters for your 55 gallon? How are you going to stock it? It's not going to be enough. I'd go with a canister filter.
CO2 tests? Drop checker. Search the DIY forums. There's information about the recommended levels of CO2 in that thread. With DIY CO2, you'll always (pretty much) be supplying less CO2 than the recommended levels, so controlling the levels of CO2 going into the tank won't be too big of an issue.