1. Fixing clip installation - can be used for sliding open, no tank cover fish tank2. Velcro installation---can be used for closed fish tank with tank coverusage notice:1. About the battery: The feeder uses 2 AA batteries, which can last for 2-4 months depending on the number of feedings.2 About the feeding amount: the feeder can be set to once every 12 hours and once every 24 hours. The opening of the feeder can be set according to the type of your fish food. It is recommended to feed less and more meals, and slowly adjust the reasonable feeding amount to avoid overfeeding and polluting the water quality.For example: Feeding consumes 2g at a time, 2 times a day, filling the snack box can automatically feed for 12 days, filling the large food box can automatically feed 25 days, the capacity of the snack box is 50g, and the capacity of the large food box is 100g.