Is the tank established? One thing I do to establish a new tank is live sand, live rock, and a piece of store bought shrimp let that sit and check your nitrate, nitrite, and amonia lvls periodically till its all evened out. At that point you can start adding your fish but add them a couple at a time to keep from having a chemical overload. Add two or three let sit for a few days check lvls add some more, the way I used to do it is I had a seperate quarentine tank and seein as how it is reccomended to keep them in a quarentine tank for two weeks set a couple in there 2 weeks later add them to the tank add a couple more to the quarentine tank monitor both tanks the following two weeks repeat the cycle hope this helps.