If you were talking about anything but a wrasse, I'd say, yes, you have trouble. However, wrasses pretty much DO hang around the bottom, often hiding away, frequently burried in the substrate. If you didn't know better, many times you'd think they were dead. They can be shy fish, so the difficulty you are preceiving, may just be that some shyness is going on. You didn't say why you are doing a copper treatment?? Copper depletes the oxgyen levels in the tank, and marine fish needs LOT of oxgyen. If you are treating this wrasse for some reason other than obvious parasite investation, then stop doing this. Add more air to your tank by dropping some airstones in the water. Get that water circulating and more o2 going and see if behavior improves. Wrasses like to come out at night when the lights are off, and will frequently bury themselves in the sand at other times. Is your substrate deep enough to allow this fish to bury which is his natural way doing things? If not, then give him some more sand! Good luck!
