Ok, I'm starting to look ahead to make the right moves. I want to fill up all of my space in my 75 gal tank. The entire top layer is SPS, just below I've started my Monti Caps. Now in the middle region, I have Chalise, Favia Etc. In the bottom areas on the rock, I have started many zoos and a few palys. In 3 of my corners on the sand, I have Euphyllias. One Bright Lime Green Calustrea in the back of my cave where the light begins again. I want to start with some Yumas and Ricordeas and a couple clams all on the sand. A couple Trachyphyllias some Duncans. How far will the Acans have to be spaced from anything ??? What about the Trachys and open brains ??? I have had in the past and know all about Galaxias and Hydnophoras :O) Are any of these others as nasty ???