i have a 55 gallon tank, i first started it about 6 months ago. the only fish in it right now is the blue tang,2 percula clowns, 12 blue leg hermits, 10 turbo snails and 2 yellow tailed damsels that i bought near the end of cycling the tank. a freind told me the damsels were the best way to start because they were good strong fish. i have around 35 pounds of base rock and around 20 pounds of live rock in it. i have found that when i turn all the lights out, and wait to check on it for a couple of hours, the tang will be out but no more than an inch or so from his hole. i originally bought the blue and a yellow tang. the store i bought it from said it would be ok if i put them in together at the same time. but the yellow tang diedovernight. al water test said ok. i even took a sample back to the store to get tested and they said it was ok, but the stress level was a bit high. they told me it wasnt anything to worry about though. i put some seaweed salad in the tank for it but clowns seem to like it so i cant tell for sure if the tang is eating. i have read that they stuff theirselves under rocks when stressed but nothing seems out of place in the tank. i mean water seems good, fish getting along good.