Are red tailed sharks like gold fish?
No, you must not do it. First of all, goldfish should never be mixed with tropical fish, because tropical fish require warmer temperatures, as goldfish require colder temperatures. These fish really don’t do well in small tanks because they are basically carp and carp have a nasty (but true) reputation for being dirty fish. In small tanks, such as your 20 gallon, the waste has no room to dissipate and your fish will be poisoned by its own waste. Red Tailed sharks can be nippy, so your goldfish’s tails would be prime targets. They also prefer tanks with large surface areas so that there is plenty of room to swim. Additionally, they’re jumpers that spook easily so you’d be almost guaranteed to find dried minnow on the floor if you try to house it in a small tank.
