How often should I feed my tadpoles and how long should I leave the food in the water before removing it?

I believe I have bullfrog tadpoles in their 2nd year; they have hind legs only. Also, how often should I clean the water? Should I have a filter set up to keep it %26quot;sparkling%26quot; clean, or since they like stagnant water should I just manually change the water and how often? And what should I use for the floor of the aquarium. I've heard sand is better than gravel but the water always looks dirty with the sand.How often should I feed my tadpoles and how long should I leave the food in the water before removing it?For tadpoles in an aquarium set up you need to clean the water a least once a week and take out any food not eaten at least in one day. I would feed them once a day, twice if you feel they will eat more. You just don't want the food to start decomposing and raising ammonia levels in the tank. Sand is great, but you always have to wash your sand before you add it to the tank, rinse it with water til the water runs clean. The tank will be cloudy the first couple of days. Filter are good, only to help remove wastes and chemicals and help the beneficial bacteria population. It may also be a good idea to add an airstone. Tadpoles may live in stagnant water, but they like freshwater.