physical Water Levels in a Drilled Tank & Sump

Question
My husband picked up a 90 gallon saltwater tank today complete with fish. Now we're putting it back together. We've never had a drilled tank with sump before. The drilled holes and pipes are behind a partition. I'm assuming this is the overflow. The level of this is below the level of the water in the main tank. This makes sense to me, since it has a float on the pipe. My husband said the guy had it totally full. Same with the 3 chamber sump. All I have researched says the way it is running now, on 3 different levels is optimum for max filtration and biological growth. Again - the previous owner had it full. Can you tell me what the water level should be in these 4 places? thanks!!

Answer
sumps can be a tricky business, water tends to find its own level so its a tight balance of, water flowing out the tank into the sump and out the sump into the tank.

there is no correct level for the sump really, as long as you figure out what the max water level will be if the return pump were to fail. it may be an idea to fit ball valves to the tank drain and sump rtn pipes so you can regulate the levels (thats if it doesn't already have them)

have a look at some of the marine forums, some of the guys have pics of their sumps and explain them in great detail.