Help!
My gold fish are in a 500gal above ground concrete/stone pond. They have wintered there for 4 years. I have a pump going. It may go to -18c at which time I put a heater in. I have some large stones and one cinder block for them to swim around. This spring they are dieing off on me. They develop what looks like red bruseing on the top sides of they're bodies, get slugish for a few days and die. 2 dead today and another developing the bruseing.
I have had these fish for some years and I am sad. I'll have none left soon.
Please save them!

