External parasites on FW fish?

[Delphinus]

Ok, another first for me. I have no idea what to do because I'm useless in the FW domain. If this were a SW fish, I'd be dipping the fish in FW to see if this "thing" would fall off.

Anyhow, I have no idea how long this has been like this, because this fish would *never* come out into the open. Had it not been that I am taking it's current tank down, and had to remove the rock it liked to hide under (in order to catch his tankmates), I wouldn't even have noticed this today.

First of all, the fish in question is a bristlenose plec. Although I'm not sure if the ID is correct since there are no "bristles" on the nose. Have had this fish for several years now.

First thing I noticed was that the tail ("caudal fin") seemed somewhat small, so I was suspecting fin rot. In trying to photograph the tail, however, I noticed something else. A red dot on the tail. It looks like some kind of barnacle or something like that, except red in colour. If this was a plant, it would be a "scale insect."

Any ideas what it is, and more importantly, what do I do about it?

By lucky happenstance, the fish is now on his (or her) own in the tank. Since I am taking the tank down I moved the other tankmates over to their new home today, and that's how I basically noticed this whole situation in the first place. So treatment in isolation is .. well .. basically pretty easily done.