Bettas need a larger living space, and they will be unhappy if they are too small; Bettas need to practice fighting (mirror); Bettas will be unhappy if they don’t get married when they reach a certain age; temperature difference is too large; viruses (Betta fish are generally not cured when sick, and they don’t show symptoms. They die quickly after getting sick, so take precautions on a regular basis) These are pretty much the problems