Unfortunately, when you mix water and light you get algae blooms, especially when there are nutrients. There are a couple things you can do: 1) clean your live rock and corals by hand since these are animals we're talking about - of course this requires doing that every day or so. 2) you can talk to your local fish store about an algae gone product that would be safe for your live rock and corals.
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Phishie
Site Coordinator

"An ounce of prevention is worth a pound of cure."