The nems were wreaking havoc in my 75G even though they were attached to rocks that were isolated. The bigger they got the more 'room' I had to make for them, so you might want to try a nice frogspawn or some xenia. I ended up breaking down my nano and put the nems and the clownfish in there. They're all really happy now and there's nothing stinging the corals in my 75G now.