What lighing do you have? Is the canopy completely enclosed? If so, you may be trapping heat in it.
The canopy is not enclosed, it does not have a top or back. I did this so that heat wouldn't be trapped so I wouldn't have to install fans. The lights I am using is the Aquasun T5 HO 24". In all honesty it probably isn't even a strong enough light for my tank but I had it already and can't afford any better at the moment

