use a rubber band to hold it to a rock or something you can move later, and that is heavy enough not to get blown arround. You will probably have to cut the band later, and pull it out as these things grow like weeds in my tank and will encrust a rubber band too. I got a frag six or seven months ago, and every couple months have moved the frag onto different places to start new colonies. I now have 4 colonies, all as large as the original frag and the original is 3 times the size it was before. I did all this in a 2 1/2 gallon pico but the coral out grew the tiny tank and is now in a 24 gallon.
Be careful what you wish for, as these things can take over a tank and crowd out your other corals. I sell my frags back to the LFS
for credit. The 24 gallon (JBJ delux) is arround 5 wats per gallon the pico is 9.6 The do well under both. I think water flow is more important than anything for these guys - moderate is best. Not too strong, but you should see the stars 'waving' in the water.