The reasons why Black Mary fish attacks fish and how to deal with them:

1. The temperament is too fierce. A small number of black marlies have a ferocious character and are extremely territorial, and are prone to attacking other fish. It is best to use a glass plate to isolate the overly aggressive Mary fish, so as to prevent gentle fish from being bullied by ferocious fish.

2. The stocking density is too high. When the stocking density is too high, the dissolved oxygen content in the water and the feeding food cannot meet the needs of each fish. At this time, they will attack other fish in order to compete for enough living space. You can change to a larger fish tank that can meet the needs of each Mary fish. If not, you can take out some of the fish in the fish tank and reduce the stocking density.

3. Not feeding for a long time. Mary fish are very hungry animals, but if they are not fed for a long time, they will feel hungry and they will attack the fish. You can put a small amount of live bait into the fish tank. Live bait is one of their favorite foods, but you should not put too much, otherwise it will increase the burden on their gastrointestinal tract.

4. Strong sense of territory. Possibly due to competition and territorial fights between black marlies. In the wild, they usually establish their own territory in a specific area of ​​a river and protect their territory from other fish. If other fish enter their territory, black marlies may attack to protect their territory and resources. It is recommended to keep Black Mary fish separately.