I noticed this about 3 months ago and thought the fish had got caught under the driftwood. I waited to see if it would clear up naturally but it appears to have spread. The areas are not raised or fluffy. None of the other fish are affected. And the fish is still eating and acting normally. I'm not sure what it is, and not sure how to treat it. 
Here's my tank info:
90 gallon
2 cascade 700 filters
nitrate 0
nitrite 0
amonia 0
ph 7.6
temp 84
50% water change weekly
2 severums
1 angel
1 blood parrot
1 black ghost knife
8 clown loaches
Here's my tank info:90 gallon
2 cascade 700 filters
nitrate 0
nitrite 0
amonia 0
ph 7.6
temp 84
50% water change weekly
2 severums
1 angel
1 blood parrot
1 black ghost knife
8 clown loaches
