Thai betta fish cannot be raised together with goldfish, because they are different in habits, body shapes and personalities, so they are not suitable for raising together.

First of all, their habits are different. Thai betta fish are tropical fish and like higher water temperature. Goldfish is a cold water fish, like a lower water temperature, and they have different requirements for water temperature.

Secondly, they are different in size. Thai betta fish are smaller in size, and their average body length in adulthood is about 10 cm. Goldfish's body size is too large, and its body length is about 20-30 cm in adulthood. There is too much difference in body shape between them, which is not suitable for polyculture.

There are also their different personalities. Thai betta fish are fierce and like to attack other fish, and their attack power is relatively strong. Goldfish's personality is mild, not too strong aggression and attack power, and generally will not take the initiative to attack other fish.

Thai betta fish cannot be mixed with koi fish because they have different environmental requirements, living habits and personalities. Moreover, koi fish is too big and likes to eat some small fish. Thai betta fish may be eaten by koi fish. If they are two kinds of fish of the same size, they cannot be raised together. Because Thai betta fish is aggressive, it is very likely to bite koi fish.