yeah you don't have to feed your bichirs live feeder fish. it's actually prefarable you don't feed them live feeder fish cause they've been known to carry a lot of diseases. you can just feed it carnivore pellets, market shrimp, crickets, smelt, silversides, and worms. if you're getting a senegal bichir then you won't have problems feeding it since they like to eat almost anything you throw in the tank. for your substrate you'd want it to be fairly smooth so your bichirs don't scratch themselves on it since they lay on the floor most of the time.