Help please. Re large goldfish with lump

[lazee]

I have a large 200 litre tank. Oldest goldfish (approx 5 yrs old) is a fancy type. Lovely tail and nearly 8/9 inches long. He has a lump on his top fin, about the size of a large raison. Same colour, if a little paler than his normal orange?
It doesn't seem to bother him but I'm a bit worried bout him?
He shares a tank with two bog standard hook a duck wins that have turned a lovely silver colour and a fancy white goldfish with the red cap(name escapes me but he's a happy chap)
We have a good filtration system and the tank is well maintained.
Is it just old age and normal lumps and bumps? All fish eating well and healthy.
Just thinking, lumpy fish is nearer 7 yrs old.

Fancy goldfish don't age as well as common goldfish so it could be age related. You'd need to do a biopsy etc to know what it is for sure, but cancerous tumours are pretty common in older fish. If he's eating, pooping and swimming well then I would just keep an eye for now. If he starts going downhill then you may want to consider humanely euthanasia (using clove oil, NOT sticking him in the freezer).

I want to hug you for actually keeping goldfish in a big tank

PS the white one with a red cap sounds like a red cap oranda.

Thanks Eau, I will keep an eye on the size of lump.