So... I'm not sure what the problem is but, I have currently a yellow tang, scopas tang, bristle tooth tomini tang a six line wrasse, a purple dottyback a pair of clowns and 1 green chromis in a 125 sps dominant tank. All my parameters are fine and these current fish are healthy and eating fine. A couple months back I added 2 naso tangs to the tank that were about 4 inches long. They decided to hide in the corner and proceeded to starve to death. Then a month passed and I figured I would give it a try again and added a healthy looking blonde naso tang. The fish was out swimming around for a few days and some what eating, then out of the blue he just began hiding under this rock and never came out and just disappeared one day. I assumed my clean up crew ate him up. What would cause such behavior in the fish? I want to add more fish to the tank but I'm afraid that they are just going to keep dying on me. Like I said all my parameters are in check, my 250W MH run 6 hours a day, water temp is 78. Please give some helpful advice to this issue.