??? what is your system, if its small run it constantly, i run a small fan even when the lights go out, tell us about ur individual setup...
ok i see ur dimensions, a bit bigger than mine, maybe u want to test the temp after running an hour and then hour after and hour after see the fluctuations, maybe have a timer turn on ur filter for an hour every three hours if u dont want it on constantly...plants appreciate fresh oxygen
Its an old computer fan in the top with a hole at the bottom of one of the walls. Sorry for the lack of details I'm a new user.