What is this?

[garfy]

Ok so my eye-biter has this lump on his dorsal fin.It looks a little like a blood blister.
Can anyone shed some light on this.
He is swimming fine,eating well and acting perfectly normal.

 

[JryanM]

Could be a parasite but I'm not the expert I'm sure someone else will chime in.

 

[garfy]

Here are a couple of pics not sure if they help.

 

[Andrew McFadden]

I can't see what your talking about is it that purple looking thing

 

[garfy]

Yes the purple lump