My 29 gallon biocube tank has been up about a year, right now in the tank I have a maroon clown and a yellow tailed damsel. The problem with the damsel is that its head is missing some scales, and is looking a little white. I have not seen it rubbing its head on the rock so have no real idea what could be causing it. I cant post a pic right now but in the morning I will. My perimeters are 1.023 salinity and ammonia is zero, nitrite is zero, and nitrate is 10ppm. The maroon does not show any of the same signs but has only been in the tank for 3 days. I don't believe the clown is bullying the damsel but I could be wrong.