Dual Food Box Optional - 100/210ml: The 210ml large capacity food box can hold 100g fish food while the 100ml small one can hold 52g fish food. Choose one according to your going out time, keep enough food to feed your fish when you go out. Manual or Automatic Feeding: The automatic mode can set the time reasonably, feeding every 12 hours or every 26 hours, helping you to feed automatically when you are on vacation or business trip. Meanwhile, one-click manual feeding will not affect the preset times. Two Installation Methods: For open aquarium, fix the feeder with the clamp, install it on the glass wall of the aquarium; for closed aquariums, attach the Velcro on one side to the aquarium lid, the other side to the base of the feeder, and stick the two sides together. (Note: When using Velcro, you need to wipe the surface clean, then fix it, and finally install the feeder.) Food Type Selection: This timer feeder can only be used for dry food. Ideal for pellet, strip and flake fish food. Please place it above the upper tank to protect the food from moisture. Then fix the tank lid, leaving only one hole. Put some aquatic plants in the hole, drop the food into this hole, and the fish will come to eat the food. Operated by 4 AA batteries (not included): When cleaning the food box, simply remove it, rinse thoroughly with warm water, and clean the drum. Make sure the drum is completely dry before adding food.