I have recently put a dwarf gourami in a tank with some black phantom tetras. They get along fine and peacefully, but at feeding time the tetras snatch all the food, zooming around like missiles to grab every piece, and the gourami is a more leisurely feeder and ends up with barely a crumb. I'm worried he's not getting enough. How can I ensure he is not starved without putting too much food in the tank? (I have been feeding mostly flake and fish crisps, and some sinking wafers for the shrimps I have).