I have a 75 fowler tank with a Tusk, Marine betta, snowflake moray, a large Fuzzy dwarf lionfish, poropine puffer, a foxface and a small grouper. My problem is I cant put a CUC in it because it will get eaten. A sea urchin was mentioned, but I was then told it would be food for the Tusk. Any ideas of what I could put in it to keep it clean? Today I had to take out the rocks and scrap them clean. Im using i mechanical filter right now. Will a skimmer help?