leave the powerhead on, the live rock will die off if it doesnt have flow and the poop will decay on the rocks and ground. if the tank has already had its diatom bloom its ok for fish, but if not your fish WILL die. add some hermit crabs and snails to keep the algea down. if i was you i would add a kenya tree or a really hardy fast growing coral. dont add any more fish for at least 3 weeks so your tank has time to stabalize. then you can start adding fish every 4 days at minimum, best is a week in between. dont add more than 2 fish to that tank please. it is already crowded in saltwater standards. im not trying to be harsh, but if you set it up wrong in the beggining its gonna either cost more to make it right or all your fish, live rock, and corals will die and you will have a big dead fish stew.