Grass carp and guppy can't be mixed together. The specific reasons are as follows:

1. Different body shapes: Grass carp belongs to large and medium-sized fish, and their body length can reach about 30 cm in adulthood. Guppies belong to small fish, and their body length is generally only about 4-6 cm after adulthood. The difference in size between the two is too large, and guppies can't survive well even if they are not eaten.

2. Different habits: Grass carp is a cold water fish, which can accept a wide range of water temperatures. They can grow in the water temperature between 0-38 ℃. Guppies are tropical fish and like higher water temperature. It needs to be between 18-32 ℃ to grow and survive. If they are farmed together, the water temperature cannot be well controlled.

3. Different personalities: Guppies have a mild personality and will not actively attack other fish. Grass carp is lively and likes to prey on small fish, so it is easy to eat guppy.

guppy can be mixed with zebrafish, traffic light fish, lotus lantern fish, fairy fish, kissing fish, rat fish, silver screen lantern fish, white cloud golden silk fish, etc. These kinds of fish are mild in character, and their requirements for the environment are not high. If they are mixed with guppies, there will not be too much conflict. Although they are all small fish, the breeder should try to keep the density in the fish tank within a reasonable range, so as to avoid the deterioration of water quality and lack of oxygen.