Hello. I have a Spotband Butterflyfish, Chaetodon punctatofasciatus, that is not doing well. It is breathing heavy, and sitting on the bottom. Occasionally he will sort of swim to a different spot and do the same. This just started this morning. Last night everything was fine, ate at feeding time swimming and pecking at the rockwork like normal. I tested the main parameters this morning, salinity is 1.024, ammoia at 0, nitrate at 20, temp is 78. This is a FOWLR tank that's been running for about 5 years, and this fish has been in for about 5 months. Nothing else has been added since, except a new batch of cheato that I added Friday. There is no damage or spots or anything that I can see on the fish. Any suggestions? Thanks.