Why have my twosome of Salmon Tail Catfish be destroyed?

My pair of Catfish 3 yr s old co existing with immense ghost knife, & 3 gold fish & a silver tail shark, one of the catfish passed yesterday and the other looks close to its done as well. They have been strong up until presently and haven't seen any dramas in the past. Wounds are perceptible on the lateral finn, what has happened??
he got in a scuffle.
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Who have you just now added to the tank and how long ago? Also, are any of the other fish acting strangely?
I inevitability an exterior house cleaner i.e....
Answers:    Knives eat other fish. It's probably trying to do a short time ago that with your catfish. It sees them as prey.
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