2, the amount of food should be based on their needs, the accurate understanding is not to give more than they can digest before the food decays, and not to overfeed, but it is best to limit the amount of food fed in a smaller tank and try to avoid too much excess food. This is very important.
Generally speaking, there are a lot of microorganisms in Ampullaria gigas, which are used to help them digest food. When microorganisms are discharged with feces, the water will become turbid and harmless to fish. It is basically no problem to filter and limit the amount of food.