What are these white tufts at the bottom of my tank? and how do I get rid of it?

Umm... 2 bettas CANNOT live in the same tank, they rarly sell females but if 1 or bother r female it is still too small and they are competing for space ur bettas need 10 gallons becuase females need more space and the boys need 5 gallon min. upgrade and get a heater and a filter, also the white stuff is a disease ur fish are fighting and infecing the water, give the bettas back or upgrade tank space.