Rally doesn't kill coral, but corals don't like it very much. I had a nuvo 10 a while ago and my ocellaris clownfish and 6 line wrasse (i know, they shouldn't be in tanks that size, that tank is long taken down) caught it. Haven't seen a sign of it for a long time after that and i've had skunk clowns (after upgrading to a 55, keeping old rock and some water)