Aquarium automation is great for taking all of the hard work out of aquarium maintenance tasks, but it also comes at a price. Beside requiring a great deal of planning and proper execution, automated processes are also inherently risky. Automatic fish feeders fail, dumping food into your aquarium, and float valves stick in the on position, filling your aquarium with fresh water. These are just two examples of the many possibilities, so it’s wise to include fail safes in your designs. For automatic top off units, for example, using a low speed water pump that is governed not only by the float valve but also a timer is about as safe as you can get. If the valve fails in the open position, the low speed pump can only pump water into your aquarium at the schedule determined by the timer. Other devices can be rigged similarly.