Ok so I have a 40 gallon tank setup for Tang. i've had 2 frontosas in there for about 5 months. We added a Yellow Calvus later on and they lived together great for about 2 months. I moved to a new apt. got most of the water with me and the fish were fine. We then decided to add another calvus to the bunch. We added the black calvus and all hell broke loose both the calvuses started to jolt around the tank and sink to the bottom and continue to lay on their sides until they died. I check all the levels and got all the kits ive needed for an african tank. I've asked tons of people whats wrong my frontosas are fine. We soon then got a white calvus and she did the exact same thing. ALL MY LEVELS are fine I just can't stand to take another fish back or watch another fish die. Someone please help me!!!