Beta fish

 1)only One bettafish should be kept in a jar. If it is a male fish then more than one fish cannot be kept in one place. Female means more than one female fish can be kept together, but a female fish cannot be kept with a male fish. It is possible to keep a male Betta fish with a female Betta fish together for only 2, 4 days during breeding time. 

2) Betta fish require at least 250ml of water, but in my experience a fighter fish should be kept in at least 1 liter of water. It is better not to keep this fish in a very large place. It is best not to keep this fish in a place larger than 2 to 5 liters of water at most.

3) Don't run the air pump or filter in the jar or aquarium where you keep the betta fish. Yes again, do not forget to run the air pump or filter, there is a 100 percent chance of killing the betta fish.

4) Soft water should be used for keeping Betta fish, i.e. water with tds less than 250 ppm. If you use such water, the fish will be fine.

5) Be sure to light the jar for Betta fish. If you don't use light, then keep the jar with fish in sunlight for 2-3 hours, otherwise the color of the fish will be lost and the fish will be sick. Take care that the water does not get too hot.