large white spot on tail

Question
I have a singe 6 year old albino rainbow shark (about 6" long) in a 25 gallon tank by itself.  I've had it for 6 years now, and I noticed a single large white spot like a whitehead pimple at the base of the tail. It is not moving, and it's not cottony. Previously I used Rid Ich, and melafix for one week and it appeared to get smaller, but now, after several weeks it got larger.  Fish is not in distress and cannot find any source to identify it.  Can ich appear as a single large spot - about 3 times the size of this dot.

Answer
Hi Susan;

I don't think it's ick. I've seen things like that before and they tend to just come and go. Sometimes it is a scar from an old injury or even just a blemish. Make a few water changes to help boost his metabolism. It may just go away on it's own.

At Your Service;
Chris Robbins