Large Lump On Side Of New Fish

It's the fish in the middle in both photos. Looks likes a sort of bubble inside the fish.

I've had a search online but can't find anything similar, only people describing this symptom but not getting any answers to what it is! I've put it in the shrimp tank for now, should really have euthanised as it's too cold in there really.
I'm a bit cross I didn't see it in the shop, but I guess you look a lot more closely when you are acclimatising fish in your tank.

That's good news. But I'd still keep it away from the other fish till you are sure what it is. Shrimps don't tend to catch fish bugs and vice versa so it and the shrimps should be safe together.

Day two, lumpy fish still alive, still spending all it's efforts trying to swim through the wall of the tank. Not interested in the bloodworm the others are going crazy over in the aquanano.