24/7.. Also I have heard that turning it off for any period of time and then turning it back on, it can release some bad stuff back into the tank. Unless it was cleaned while it was off.
I read somewhere that a heavy skimmer removes some good stuff for filter feeders. Didn't think it held to much water but just wanted to get everyones opinion.
it does strip alot of nutrients from the water....which is why there are actually corals which will do better in a tank which is not skimmed.......i still run my 24/7 though.....figure weekly 10% changes with good salt should handle that
I turn mine off when I feed just because I found alot of the myis shrimp get down into the skimmer and either clog it up or just get sucked up inside and wasted. Plus i trained everyone ( i think) that when the pump/skimer go off its feeding time.
I used to run mine 24/7 and just recently put it on a timer. I was having problems with micro bubbles after I added my sump. I realized that my skimmer was causing a lot of them. Now my skimmer only runs when my lights are off.