Oscar white lining natural or fin rot?

Hi all, I’m new to this forum, and relatively new to aquariums, although I have a fisheries biology degree.
I recently rescued an Oscar from an outdoor pond and have it in quarantine.
My question is about the white lining around it’s fins. It is otherwise healthy and active, and the water parameters are all good. Could this just be natural coloring, or is it the beginning of fin rot?

thanks!

I think that’s natural , I’m sure my Oscar had a thin whit line run round his tail fin

Agree that its natural colouring, have seen many (tiger) oscars with white tipped fins

Hello and welcome to the forum!

Yes, that's completely natural - I see the Oscars at my LFS displaying those colors all the time.

It's excess mucous caused by poor water quality or something else irritating the fish.

Check the ammonia, nitrite, nitrate and pH of the tank water.

Do a 75% water change and gravel clean the substrate every day for a week.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

If there's no improvement after a few days of water changes, add 2 heaped tablespoons of rock salt for every 20 litres of water. Keep salt in there for 2 weeks.

Thanks, all! I had a fish vet look at him and confirm it is natural coloration.

If you want another puzzle, have a look at my next post about clear jelly balls found in my tank.