My daughter has a a two year old, 60 litre tank with lots of smaller fish, the neons are about the largest, endler guppies, dwarf anchor catfish, bumble bee shrimp, etc..
10 litres of water are changed about every 2-3 weeks, and there are live plants that are doing well and have to be frequently trimmed. All tests of the water were done frequently for the first year, but only once every two months now and readings have always been very good, after the first 6 months anyway!
The neons started out very small and now are the largest fish in the tank, about 2 years old. One always had a slight curvature of the spine, but apart from this disability seemed OK until yesterday when I noticed his body near the rear tail fin was quite white and slighlty extended (wider than it should be). Although he was swimming around happily, I decided to remove him from the tank to stop any contamination. I then noticed another neon had slight white spot in the same area. It is really only a few scales. Is it a disease or is he just getting "grey" as he gets into the later months of his life?
What I need to know is, should I remove him too, or treat the water with something?
Please see photo below.