Planted Tank Enthusiast
Join Date: Feb 2012
Location: Edmonton, Alberta
IMO, you are going to get poor front to back coverage with a single doublebright light.
I've got one on my 18" cube and I find it really only provides effective light to about half the tank, leaving dark bands front and back if I center it.
For a 24" cube I'd strongly suggest using two doublebrights if that is the way you end up going.