Goldfish has red sores/lumps on back

[casdeswinchester]

Hello, I've had my white goldfish for about 3 months, they are in a 100l tank and when they get bigger I plan to upgrade it. At the moment they are very small and recently I added more goldfish, a few days later the white goldfish has red lumps on it's back. The white goldfish has always been sitting in the corner of the tank ever since I got it but does eat and poop normally. Is it a disease passed on from the new goldfish or is it something else? Thanks

 

[Colin_T]

it looks like someone has pulled anchorworm out of the fish and the red spots are the sores left over.

do a 75% water change and gravel clean the substrate. make sure new water is free of chlorine/ chloramine before it's added to the tank.

add 4 heaped tablespoons of rock salt, sea salt or swimming pool salt, per 20 litres (5 gallons) of tank water. keep the salt in there for 2 weeks and see how they go.