i think it all depends on what you have in the tank. some corals, clams, oysters, feather dusters, gonipora, sponges, need some nutrients in the water. what do you have, or plan on keeping?
All I have is 4 damsels, fire fish, colt coral, some shrimp (skunk, 3 pepermint, and blood), and a big clean up crew. Would like to get some pulsing xenia soon.
depends on the skimmer =berlin are rated 400g some. But they can't IMO they are junk. An euroreef rated at 300 will overskim a 40g tank But a berlin imo won't. But if you have a good fish load and feed heavy I wouldn't worry.I have heavy/good skimming and have mass breeding tube worms.mass pods ,3 types of snails breeding ect ect. Just depends on your system. but a 4' skimmer on a 40g maybe. But a 2' skimmer on a well fed 100g i doubt it.
That hurts me!! I love my berlin turbo skimmer. Anyway it is easy to over skim a tank with a downdraft skimmer. but with a standard skimmer it is harder to do.