Anyone know what this is and how to treat it? One has a white lump near its eye, the other some white stuff at the end of its fan tail. Both usually in a pond with others but currently quarantined in a bucket each.
It looks like a fungal infection,it is common for pondfish to get this or other types of problems in the spring before the imune system of the fish starts working(it takes some time for the water to warm to a level where the imune system starts to funktion)
The common treatment for this is to add aquarium salt so the consentration is 0,3% of salt in the water,and to increase the temparature to 20C.
If you are able to treat the fish in a separate tank you can add medication to the water i use tetra medica general tonic in addition to adding salt.
To limit the production of waste products it is best to only feed very little food every 3 days,be sure the water is well oxygenated to limit the stress for your fish.
A salt consentration of 0,3% is not dangerous to goldfish or koi and can be continued indefinitely.
Adding medication to your pond is something i will advice against as it will destroy the biological balance in your pond.