rash

[liamoi]

A small barb in one of my tanks seems to have some kind of rash (a bit like white spot) on its tail fin. It appears to be the same colour as the tail (orange) only a bit darker. I can't see any more of it on any other part of the fish or on any other of the fish in the tank. The fish seems to be behaving and feeding normally, though maybe flicking a bit. Does any one have any idea what this might be and how best to deal with it!?
Cheers.

[jeffs99dime]

a pic of it would help greatly

[Lady Hobbs]

A couple of my platies have small spots on their tail fins too. I thought at first it was a fungus but it's not. Just a mark of some kind. You almost have to look thru the tail into the light to see it.