When introducing a new fish to your aquarium, turn off the water pumps and powerheads so that the stressed and confused animal doesn’t get sucked into the impeller and fatally injured. New fish have a lot of trouble adjusting to a new environment, and chances are they haven’t seen your fancy water pump during their brief trip from the ocean to your aquarium. The scared fish, when first introduced, might mistake your aquarium equipment for a secluded cave in which it can hide. Unfortunately though, this is probably the most dangerous place to be, and fish-pump interactions almost never go well for the fish. If you don’t want to turn off your pumps completely, they can also be slowed down so that their suction force is less. Obviously this controllability is limited to specific brands and models.