Newbie to marine

[Bloodasp]

Most corals have a symbiotic algae living in their cells that provide them food. You don't necessarily have to feed them but they do get a lot of benefit from being given something from time to time. That's the reason why lighting is such an important element in a reef aquarium.
An overflow is a part of your system where water from your main tank gets transferred to your sump.
Anyway I don't know what I said either I was just typing what is popped into my head at this very moment reading this thread.