Become a Sponsor

Information Pages:
Marine Aquarium
Articles/ FAQs/Index
Freshwater Aquarium
Articles/ FAQs/Index
Planted Aquarium
Articles/ FAQs/Index
Brackish Systems
Articles/ FAQs/Index
Daily FAQs
FW Daily FAQs
SW Pix of the Day
FW Pix of the Day
Conscientious Aquarist Magazine
New On WWM
Helpful Links
Hobbyist Forum WetWebMedia Forum
Ask the WWM Crew a Question
Search Feature
Admin Index
Cover Images


External Pump Impressions

By Steven Pro

With the increasing popularity of sump-based systems and closed loop circulation, a thorough discussion of external water pumps is warranted.  External pumps have several pluses in comparison to internal ones.  External pumps usually impart significantly less heat than internal pumps.  This can be extremely important for reef systems with their high intensity, high heat lighting systems.  Plus, many are more powerful than internal pump options.  As such, most larger aquaria are designed to incorporate at least one and sometimes numerous externally mounted pumps to provide the majority of the displays circulation.

 Custom Sea Life Velocity T4:

Custom Sea Life (CSL) went out of business a while back, but these same pumps are now available under a couple of names, including Poseidon and Blueline. These little blue pumps are super compact and extremely quiet.  Their diminutive size is the most striking feature when first seeing one up close.  That is until you touch one that is running.  Man, do they run hot!  I was literally unable to keep my hand on the pump long enough to count to three, one one-thousand, two one-thousand, three one-thousand.  I couldn’t get past two before I had to yank my hand away the heat was so intense.  That concerns me for two reasons. First, I am concerned with how much heat this imparts to the water.  Second, I am concerned with what impact this has on the pump’s life.

E.G. Danner/Supreme Mag-Drives:

While a lot of people know that these pumps can be used submerged, they also can be mounted as an external pump.  I have used a number of these pumps in this manner and have found them to function just fine.  They are very reliable, but their strongest selling point is how inexpensive they are.  They are one of the cheapest pumps available!  They do have their downsides though.  They are not the quietest pump.  And, they likely impart more heat to the water than other external pumps.  Still considering their price and reliability, they are an attractive choice.

The only other potential problem people have with these pumps is salt creep.  They are prone to tiny leaks, resulting in some salt residue around the intersection of the pump housing to the impeller cover if the o-ring is not seated in place properly.  This can usually be corrected easily enough by unscrewing the four screws holding the impeller cover in place and reinstalling the o-ring.  Otherwise, maintenance is rather minimal on these pumps.


Eheim is another brand known mostly for submerged applications but they may also be mounted externally and they are extremely reliable whether used in or out of the water.  Unfortunately, that reliability comes at a price.  Eheims are rather expensive, especially considering the modest flow rates they produce in comparison to their purchase price (see my Pump Comparison article here:  Still though, they do have their place.  If I was looking at the multitude of aspirating, needle wheel driven protein skimmers, I would favor those using Eheim pumps because of their outstanding reliability.

Gorman Rupp Industries (GRI):

A GRI pump in use.  A powerful pump at a reasonable price.  Photo by Steven Pro

I have not used many of these pumps but I have been very pleased with the few that I have used.  They are relatively quiet, rather powerful, and reasonably priced.  And, for those who consider it important, GRI pumps are American made.  I just have not used enough of these pumps to feel comfortable recommending them just yet, having only ever used four.  But my limited experience would seem to indicate that if one were to purchase one of these pumps, they would not be disappointed.


I don’t have much to say about these pumps.  Iwaki are my default choice.  They have been making very reliable pumps for a long time.  Most of the Iwaki line is available in with either American made or Japanese made motors.  I have only ever used the Japanese made models. American made models are reputed to be noisier than their Japanese counterparts.  So, while the American ones are considerably cheaper, that discount come at a price in terms of added noise.

The original Quiet One was a compact, nearly silent external pump that produced a lot of flow.  Unfortunately, they were also prone to overheating and shutting down.  The new generation of submersible Quiet One's can be used submerged or externally and are available in a range of sizes.  Photo by Steven Pro

 Little Giant:

These were the first external pumps I used and as such, I had nothing to compare them to.  But looking back, they were not particularly quiet pumps.  Actually, they were relatively loud and annoying.  They also seemed to rust rather easily in the high humidity environment of an aquarium stand with a sump inside it.  These pumps are reputed to be fairly reliable, are available in a range of sizes and are relatively inexpensive.

Rainbow/Lifegard Quiet One:

The current line of Quiet One pumps are built for submerged or external use.  The previous generation Quiet One pumps were for external use only and are the only ones I am familiar with.  They were very quiet, as their name would suggest, and did not seem to impart a significant amount of heat to the water.  They were also rather compact for a pump capable of putting out 1,000 gph.  Unfortunately, the old Quiet One pumps were plagued by overheating issues that would cause the pump to shut down until it cooled off.  Even though the new pumps are a completely new design, I have not tried them because of my previous poor experience with the old ones.


There are a multitude of external pumps currently available and I have only had the opportunity to try a few.  Still though, I have found several that I am happy with and comfortable recommending to others. Japanese-made Iwakis are by far my favorite brand of external pump.  They have been around for a long time and I have yet to be disappointed with one.  For the price conscious, my next choice is the Mag-Drive pumps.  I have found them to be quite reliable and their price makes them hard to pass up.

About Gear Selection for Circulation on WWM

Related Articles: Submersible Pump Selection, Efficiency and Price Assessments by Steven Pro, Circulation, Aeration, Inexpensive Wavemaker Impressions, by Steven Pro, Water Flow, How Much is Enough, Marine System ComponentsRefugiums, Central FiltrationFlow-through Live-holding Systems, Refugiums, Business Set-Up

Related FAQs: Pump Selection 1, Pump Selection 2, Pump Selection 3, Pump Selection 5, Marine Circulation 2, Marine Circulation 3, AerationPumps, Powerheads, Installation/Arrangement, PlumbingMake Up Water Systems, SumpsRefugiumsSurge Devices


Featured Sponsors: