running co2 with lights off ?

[gregzz4]

What kind of Rainbow did you lose?
I went through 1/2 a school of Threadfins before I figured out it was chlorine-burnt gills. I was adding Prime as the WC happened.
I then started pre-mixing and problem solved. It did quadruple my WC time though as adding 50g from a 15g tub took much more time.

+1 to wasting CO2 @ night
Running it @ night can cause deaths if you don't have enough surface agitation/air injection -stones, venturi powerheads etc.
Having your CO2 on a timer set to turn off about 1/2 hr before lights out and come on about 1/2 - 1 hour before lights on is usually the best recommendation.