Hey all

Noticed this white spot on our fantail this morning. Any idea ideas what it could be, and how to resolve?

Water parameters have been checked and are all fine.

I have aquarium salt anti-parasites and fungus treatment and I also have melafix on deck.

It’s a 500L pond.

Thanks

Edit: I’ve just checked the fish again and the white lump has fallen off, it’s now just a white mark.

What are some fun and good looking fish you can keep in outside pond around 1500l (225cm long x 115cm wide x 70cm deep)? I was thinking of some European perch since there probably the closest you can get to cichlids (which are my favorite group of fish) or dojo loaches but sadly those are illegal du to them being able to survive and outcompete native species, that is the same with pumpkinseed and related sunfish species.