Possible problem?

[jobu28]

Trying to figure out what is wrong if anything. The pic where he looks ok was taken this past Saturday. The second pic was taken Tuesday. On Tuesday I came home from work and was like what happened. He looked like he had been bleached. I tested the water(results below) and pretty much just left him and hoped for the best. Called around to some friends to no avail. Wednesday he looked a little better but still figured him to be a goner. Today came home from work and is all normal looking. Tank has been up for about 6 months. Any suggestions?
sal 1.018
temp 78
am 0
nit .50 (not sure why)
nitrate 60

 

[usirchchris]

Nitrites at .5 would be your problem. Ammonia and nitrites should always be at 0, and either are very toxic to fish. Fins are looking a bit ragged as well...is something picking on it, or is it from the water quality? Your salt is a bit on the low side...I would raise it to 1.020 and your nitrates are getting to the high end at 60. Nitrates are nothing to get real hyped up about, but exposure to high numbers for long periods of time could cause stress.