I haven't used covers for a looooong time. It's amazing watching them explode under a MH lamp. It would be affecting the light to a degree, get rid of them! I think this deserves a poll....
ok gone ! the only thing they are good for is evaporation reduction and splash/salt deposit reduction.
the cons are greenhouse effect + no airflow to surface. + light has to pass through glass + salt film.
So im going to try it without.
Oh the other thing is... I dont have a sump or refugium. I understand many people are succesfull without a sump, but I figure it can't hurt me at this point to add one (well except my wallet) ~!