Well, I'm keeping it on while I'm curing, because last time I just let the rock sit without a skimmer, just water changes, and the extra nutrients and stuff from die-off made one thing grow, which fed another, etc. and I ended up with a unrecoverable "bad" worm infestation, forgot what the LFS said, and became determined to start from scratch with a bigger tank, sump, skimmer, all RO water, Metal halides, etc. so I'd rather overskim on this one, I can always adjust the flow to the skimmer.