Much like LEDs radically changed the landscape of reef aquarium lighting in just a few short years, so too has it been with DC pumps. Controllable pumps from AquaBee, Sicce, Ecotech Marine & Maxspect have all but pushed out the classic pumps like Iwaki & Reeflo from aquarium store shelves.
But with so many controllable, internal water pumps available to hobbyists what is the case for these pumps that seem to cost more than DC pumps but yet push ‘less’ water volume? There’s no doubt that when it comes to moving sheer water volume the DC pumps are really great but external pump are untouchable when it comes to one parameter, and that is pressure.
When a DC pump is rated for 1500 gallons per hour that metric is at zero pressure and depending on the model you’ll be lucky to get 900 to 100 gallons at a typical five feet of head from the sump to the tank. But if you have an 1150 gallon external pump which is pressure rated you’ll probably get 1050 gph when it’s all plumbed up and running a typical reef tank. So it goes without saying that if you have to pump any distance or height you really should be using an external pressure rated pump.
Furthermore if you’re putting ANY kind of outlet accessory like an eductor, penductor, flow accelerator or ‘random’ flow generator with a DC pump the back pressure will put a huge hit on the volume coming through the tank. However if you’re using a pressure rated pump, you can actually convert the energy from the pump’s pressure into extra water flow within the aquarium using those same kind of attachments on a pump like an Iwaki.
For more information about the benefits of external pumps, our Reef Aquarium Neighbor Scott Anderson of Mile High Reefers has a great video he made for PGS Aquatics. In this clip Scott discusses the unique benefits of the legendary Iwaki external pumps and the reasons some reefers should consider this style of pump over what is more commonly found at the LFS.