if you let the bag float, be sure to keep an eye on th etemp in the bag. Most lights will heat the water in the bag a lot hotter than the actual temp of the tank. Floating in the sump is an OK idea. Unless the water parameters (mostly salinity) are drastically different between your tank and the tank where the anemone came from, I lik eto open the bag, pour 1/2 - 3/4 of teh water out, and then add your water back to the bag a little at a time (maybe 25% of what in the bag), until you get the bag back to where it was.. Maybe a little more.. A drip method will work well too.