I have 9 green neon tetra in a 55L tank. The fish have been in there between 3 and 4 weeks and all has seemed fine. Yesterday whilst watching them feed my partner noticed a black spot on the side of one of them. I've googled everything I can think of and can't really find anything so thought I'd put a photo on here to see if anyone has any ideas.
Any advice is very much appreciated. Cheers.
Any advice is very much appreciated. Cheers.