The first group is a high flow motor driven water pumps for high flow and high pressure applications. The Seahorse and Seaflow pumps are designed with a pre-filter, self priming chamber to allow them to be placed above the water level. These pumps have a large intake/outlet, 1 ½” to 2” fittings and are rated by Horse Power. The largest units can be wired to 220V outlets to reduce cost of operation.
The second class of submersible/external water pumps has a magnetic drive and impeller drive but more importantly, they also have true plumbing fittings for the intake and outlet. This allows you to place them “in line” with water tight fittings. These pumps, such as the Mag Drive, Quiet One, Hobby Pump, or Hy-Drive Pump, are not self priming. They must be placed below the water line with the intake line flowing to the pump via gravity (siphon). When used externally, they will usually require a bulkhead fitting through the side of a sump system or need to be located on the floor with an intake and return line coming from the aquarium. This line must be primed once to start the flow.