Double food box available - 100/210ml: The large 210ml box holds 100g of fish food, while the smaller 100ml box holds 51g of fish food. Choose one depending on the time of year you are out and it will hold enough food to feed your fish while you are out. Manual or automatic feeding: The automatic mode can be set at a reasonable time to feed every 8 hours, 12 hours or every 24 hours to help you feed automatically when you are on holiday or travelling. Also, one-touch manual feeding does not interfere with the preset times. Two methods of installation: for open tanks, attach the feeder with clips to the glass wall of the tank; for closed tanks, attach one side of the Velcro to the lid of the tank and the other side to the base of the feeder, attaching both sides together. (Note: When using Velcro, the surface needs to be wiped clean before attaching it and the feeder installed last.) ;Food type selection: This timer feeder can only be used for feeding dry food. It is ideal for pellets, granules, strips and flakes of fish food. Please place it on top of the tank at a higher level to protect the food from moisture. Then fix the fish tank lid, leaving only one hole. Place some water plants in the hole and let the food fall into this hole and the fish will come to eat the food. Operation by battery (included): When you clean the food container, simply remove it, rinse thoroughly with warm water and then wash the drum. Make sure the drum is completely dry before adding food.