Good question well put. I think they are goldfish of some kind, but i'm only guessing. They have been fed this morning, but there was no sign of them but given I have lived here more than 3 weeks (?) and had no idea they even existed, that is nothing to go by.
Here are 2 of them, the 2 I caught and rescued due to them being in distress from lack of oxygen in the remaining water in the pond (which was thick with mud, debris and stank to high heaven.) The 3rd looked like the 'normal' one but I wasn't able to catch it.
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2 of the fish
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and the fish pond after I had re-done it.
PS I know nothing about fish, or keeping them or fish ponds!