Planted Tank Enthusiast
Join Date: Aug 2006
Location: Cincinnati, Ohio
How many gallons? 2 days is an incredibly short time I believe to be without CO2. About 6 or 7 months ago I totally lost interest in the hobby and critically neglected my 29 gallon tank. No ferts, no fish or livestock, just light and top-offs. Even the surface was nearly covered by plant matter blocking a lot of the light.
The Riccia looked really grim but it's starting to recover now. Ludwigia Repens was okay, and Dwarf Sag was practically taking over the tank and even the glosso was still okay. I guess my point is over 2 days, I doubt you'll even notice anything in the plants. I wouldn't worry at all about your plants surviving a few days without CO2.
Depending on the tank size and the amount of light, I'd perhaps throttle down the amount of light, especially since you aren't adding fertilizers yet. Without fertilizers or CO2 in a high light setup, my first concern would be an algae issue and not necessarily the plant health. Perhaps others in similar situations may chime in here too, but I don't think 2 days give or take a few days is anything to worry about, so you could probably just use a judgment call to decide how much to cut back.