Black spot on foxface lo

[robo100]

I have noticed that my foxface lo has a black spot near the tail that is about the size of a dime. This spot is on both sides of the fish. Is this normal? The fish seems very happy and other than the spot doesnt seem to have any problems. Here are my parameters:

Am: 0
Nitrite: 0
Nitrate: 10
PH: 8.2
Temp: 76

If need be I can get a picture of the fish.

 

[Krish]

If you google some pictures of foxfaces, you'll notice some of them will have the same black dime sized spot by the tail so I would think that is common for them. Just a thought though...I'm sure someone else will chime in, but in the mean time here's one photo I googled

http://www.saltwaterfish.com/site_11_03/images/275_foxfacetang1.jpg