my harlequin has a very large white fuhzzy spot on his nose and is swimming slowly with his mouth open should i put him in a breeder net or what help please
If you dont have a picture we cant tell exactly what is it but what other fish are in the tank?
It may be ich and there are a few different treatments but the cheapest is epsom salt and heat but some fish are sensitive to salt hence me asking what the other fish are
It sounds much more like cottonmouth, than ich. Cottonmouth is a fungus and can spread to the others, if not dealt with.
If you have a proper quarantine tank, then it would be a good idea to pull that fish out and treat it with some anti-fungal. CAn't recommend any meds though available in the UK.
I saw your stocking list in a different thread, and have to say that the cause of all the problems you are dealing with is that your tank is overstocked. That's far too many fish for a 96L tank, and some of those fish are not appropriate for a tank that size, specifically the flying foxes and the danios.
Do you have a picture of the harley's nose and mouth? That would be best in determining if it is really a fungus or if it is something like columnaris which is bacterial infection that is very contagious and often referred to as "cottonmouth disease" and "saddleback disease". It tends to pop up in tanks with stressed fish and overcrowded situations which is what you have.