I inherited a betta fish from a cousin of mine, and I've had him for quite some time now. He's always been a very energetic fish, who was always happy to see me, and loved to eat. Now he's recently been very sluggish and tired all the time. Also he barely eats. I know nothing about taking care or betta fish andi have no idea what to do. I've been cleaning his tank every other day because green stuff keeps growing everywhere and I've also gotten rid of his old plants. What do I do?