well its just like everything its a balance keeping it on isnt going to make them all look great. for me is i change the timer around at times. my lights and co2 and plugged in different areas so i would have to change two things. co2 is cheap i didnt want to worry about it. so now its left on. i also watched my fish and co2 levels. this is why a drop checker is great for tanks. its a visual aid to help. i am not saying dont turn it off i am just saying it isnt a must. great thing about tanks there are more then one way to do things.