So far, my saltwater aquarium requires 1540 watts for lighting, heating, and pumps, etc. I could see this growing to around 2000 watts. I plan on installing a new 20 amp breaker running to a 20 amp GFCI outlet behind and above the tank using 12 gauge wire. Probably hooking a six outlet power strip to each of the 2 outlets. Does this sound like the best setup for the situation? Thank you very much for any reply...

Well the upper number of 2000 watts would be perefct for a 20 amp breaker and wire but why plug power strips into a new circuit you are installing. You should install 6 duplexs.