MD-40RT - 822 GPH Japanese

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Why does BRS recommend this?

Anytime we need an external pump the Iwaki Japanese motors are our first choice.  There are cheaper options that work just fine, however when it comes to noise the Iwaki Japanese external pumps are class leaders and for any area where noise a concern and space is limited. The Japanese Iwaki pump is the way to go.


External pump from Iwaki, the world leader in small magnetically coupled centrifugal pump technology. MD stands for Magnetic-Drive. High quality external pump with years of research and development behind its design. Iwaki pumps offer high pressure rates in a durable, compact pump. Easily tailor pump applications because of the numerous motor/pump configurations. Japanese-made motor is designed especially for aquatic applications. Super quiet and energy efficient.


MD Series – Japanese Motor

  • Japanese motor is made from cast aluminum with a cast end bell
  • Japanese model uses a custom pump design specifically for aquatic applications
  • Japanese pumps run cooler to the touch and slightly quieter, due to the thicker material

Note: The Iwaki MD pumps' power cords do not come with the plug pre-wired.



  • Japanese Motor
  • Max Flow: 822 GPH
  • Max Head: 21.3 Ft
  • ¾” Inlet(MPT)/ ¾ ” Outlet(MPT)
  • Max Amps: 1.3
  • Motor Output: 1/12 HP


Iwaki Flow and Tech Specs


Quick Compare - Iwaki MD Pumps (Japanese Motors)

ModelPower UsageMaximum FlowMaximum HeadConnections

Iwaki MD-20RT


492 GPH

14.1 ft

Hose 5/8” NPT ¾”

Iwaki MD-20RXT


822 GPH

8.2 ft

Hose 1” NPT 1”

Iwaki MD-30RT


600 GPH

17.7 ft

Hose ¾” NPT ¾”

Iwaki MD-30RXT


1140 GPH

13.5 ft

Hose 1” NPT 1”

Iwaki MD-40RT


822 GPH

21.3 ft

Hose ¾” NPT ¾”

Iwaki MD-40RXT


1344 GPH

15.4 ft

Hose 1” NPT 1”

Iwaki MD-55RLT


1104 GPH

26.9 ft

Hose 1” NPT 1”

Iwaki MD-70RLT


1536 GPH

31.8 ft

Hose 1” NPT 1”

Iwaki MD-100RLT


2136 GPH

39.0 ft

Hose 1” NPT 1”

More Information
Input Size 0.75" (3/4 in.)
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Product Questions

Do the Iwaki pumps have a soft start? Do they need one? Is there a sudden thump and grind on startup as I find with my Danner Mag18 pump that I'm looking to replace? I cycle the return pump off/on at least once daily for feeding.
Question by: Phil on Aug 12, 2022, 1:22 PM
Hello Phil,
No, there is not a "soft" part to these pumps. There is not a "thump and grind" to my knowledge. Something you can do to help minimize loud vibrations with a pump is to put a sound dampening pad underneath the pump such as SKU 202000 or SKU 208534. Another thing to try is having the first foot of tubing coming off the output of the pump be silicone tubing. This also helps minimize vibrations and unwanted noise. Please let me know if there is anything else I can assist you with!
Answer by: Ash Hoglund (BRS Staff) on Aug 18, 2022, 8:56 AM
Would you recommend this pump for a basement sump set up for a 125 mixed reef tank i am setting up. About 12 feet of run back up tank?
Question by: Ken on Jan 3, 2017, 6:55 PM
Great question! This pump will be far under powered for that application. You would need a pump that will have around 1000gph-1300gph after the 12ft head height. For example, this pump has 822gph directly at the output and has 21.3ft of head. That means, after the 12ft high run you should expect somewhere around 400gph coming out of your return lines. :-)
Answer by: Randy on Jan 11, 2017, 1:32 PM