Cobalt MJ1200 Powerhead

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Cobalt MJ1200 Powerhead

80% Recommend this to a friend (40 of 50)

SKU: 210504
In Stock: 1,584
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Quick Overview

Why does BRS recommend this?

The Cobalt MJ line of pumps is great for auto top off systems, reactors, or low flow equipment.  These pumps are made in Italy and are much quieter in operation than similar pumps that appear to be identical.  With so many applications the Cobalt MJ pumps have some of the best value for a submersible pump. 

  • Flow Rate: 295 GPH

  • Maximum Head Pressure: 69"

  • Power Usage: 20 Watts

  • 3 Year Warranty


Full Details

The Cobalt Aquatics MJ series of pumps is the same Italian-made MJ you have been using for the last 20 years. Reliability and low operating noise have been the staple of this pump series, a principle reason why aquarists around the world have been using them for decades. After the original MJ distributor moved operations to China, Cobalt Aquatics jumped on the opportunity to work with the Italian manufacturer to continue to provide a source for this high quality product line. Mostly used for wave makers, protein skimmers, calcium reactors, nano aquariums, under gravel filters and hydroponic applications.


  • Fully rotational output
  • Fully sealed intake for internal and external use
  • Universal intake tube Adjustable hanger with cord guide and 6 Ft power cord
  • Adjustable venturi with silencer
  • Triple suction cup mount
  • Large intake screen for use with sponge

Quick Compare - Cobalt Aquatics MJ Powerheads

Model Flow Rate Maximum Head Pressure Watts
Cobalt MJ400 106 GPH 29" 5

Cobalt MJ600

160 GPH



Cobalt MJ900

230 GPH



Cobalt MJ1200

295 GPH




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  • Don't buy if you need good flow By Charles on 5/30/2017

    Has little to no flow with zero head pressure I wouldn't recommend for price it should be much better I've had cheap Chinese pumps better then this also should a barbed fitting to connect multiple sizes of hoses to it if I was brs I would not have chosen this as a brs recommends product and fills very cheap
  • Just was not for me! By CLAUDIUS on 5/1/2017

    Purchased two MJ1200. Both stop working exactly 1 day after my warranty.
    I have 2 other powerheads that I've had for years and was much cheaper.
    May work for someone else!
  • SHOCKING EXPERIENCE By Sparky on 1/28/2017

    I was cleaning this pump and plugged it in to run fresh water through it. The pump shocked me pretty good so I got a voltage tester and threw one probe in the bucket with the pump running and the other to ground. 48 volts was surging through the water.. The pump was only about 5 months old and I wonder how long it was energizing my reef tank. I did want to share this experience since the MJ's highly touted as being good. I have replaced this one with a Eheim 1048 that I've had for 15 years that was in my boneyard of retired equipment. Now that is a good pump!!
  • Awesome By Mark on 1/16/2017

    I bought a used biocube 29 that someone had already done a mess of "retrofit" diy wtf... Luckily this return pump was the best and only part I kept. Mine is an older model, but it is still pumping away like a champ one year in, plus however long previous owner had it. Made me brand loyal!
  • Awesome Pump! By Shane on 9/12/2016

    I dont know why everyone only sells the Marineland pump, this Cobalt pump is worth every penny. I've always gone with the Marineland as those are the only version sold by my local LFS, but anytime you try to restrict flow, for a reactor for example, they generate a ton of heat and noise, even just barely throttling them back. This Cobalt is silent, runs cool, and works great. I am going with these from now on. I cant speak for longevity as I havent had this pump for very long but I am extremely happy with it so far.
  • Failed after 3 weeks of use By Scott on 4/7/2016

    Maybe I just got a bad one, Mine failed after less that 3 weeks of use. I contacted cobalt directly, they said I should soak the impeller in vinegar for an hour, I did that it still did not work. Soaked it for a full day. Still did not work. Called cobalt back and they said they would send a new impeller. That was almost four weeks ago, still no new impeller
  • Great pump! By juschillin2 on 3/7/2016

    Works exactly as described. Very pleased powerful AND silent. Highly recommend!
  • Great Product! By Christopher on 3/7/2016

    This pump is unbelievable! Super Quiet! small footprint considering mine sits in the tank.
  • Great pumps By GLC on 12/16/2015

    These are tried and true workhorse pumps. I use them for multiple purposes and they are extremely dependable and quiet. The Cobalt brand is much quieter and the build quality is superior to the Marineland version.
  • Good Buy By Greg on 12/13/2015

    Works great ....Perfect for my carbon/gfo reactor.
  • So far so good! By Adam on 12/12/2015

    I purchased this power head to power my BRS dual reactor. So far, it's quite and works as advertised. So far so good!
  • Workhorse By Virgil on 11/30/2015

    I have 3, my oldest has been running for 3 years with no problems


Ask a question

Product Questions

In using this with your mini reactor, is the pump large enough to push the water from the display down 35 inches, (inside the stand) then back up the 35 inches back to the tank? Or should I be looking at something larger? The tank is only 45 gallons and is an all in one, hence why I want to put it in the stand, (back siphoning an issue I am aware of).
Question by: Lola on Jan 31, 2016 4:42:00 AM
Great question!
In this pump it has a maximum head height of 69" meaning the flow after pushing the water back up 35" will be greatly reduced. We would recommend a larger pump if possible such as a Sicce 1.5. I have included a link to the pump as well as the adapter to connect the pump to the reactor tubing.

1⁄2" Male NPT x 1⁄2" Push Connect
SKU: 100003

Syncra Silent 1.5 Pump (357 GPH) - Sicce
Answer by: Connor (Admin) on Feb 10, 2016 3:13:00 PM
What all do I need to connect this pump to the BRS Dual Reactor for gfo and Carbon besides the 1/2" tubing?
Question by: Eric Hott on Jan 10, 2017 9:01:00 AM
Great question! All you will need is a 1/2" push connect fitting. You can either use the straight union or a push connect inline ball valve. I've listed both of those in the links below. :-)
Answer by: Randy (Admin) on Jan 11, 2017 4:03:00 PM
Can this be used as an external pump if you plumb the input?
Question by: Aaron on Jan 22, 2016 11:20:00 AM
Great question!
This could be used externally however plumbing it would prove to be a challenge as it does not use barb or threaded fittings and would need 1/2" ID tubing to connect to it. Keep in mind this cannot pull water, only push, so when plumbing the water will need to naturally feed into the pump. Feel free to let us know if you have any further questions!
Answer by: Connor (Admin) on Jan 28, 2016 1:44:00 PM
Im looking at this pump to replace my Rio on the CPR bakpak skimmer, does this come with everything need it make it work. Im gonna be honest I'm not the best at mods. Thank you.
Question by: Adam on Jan 22, 2016 6:48:00 PM
Great question!
This pump will come with a standard impeller and will not work as a skimmer pump unfortunately. If you have a replacement impeller which can work in a MJ1200 this may work? Feel free to let us know if you have any further questions!
Answer by: Connor (Admin) on Jan 28, 2016 3:34:00 PM
As I need to ensure that space is available within my existing sump, what are the "footprint" dimensions of the MJ-1200 pump?
Question by: Patrick S. on Apr 14, 2014 12:21:00 AM
Hey Patrick,
Assuming the output is up and your not using any of the suction cups, brackets, etc the pump is about 2" wide and 3.5" across, though keep in mind with that later number you will want some extra room so the water can actually enter the volute so I would go with more like 2x4 at the least.
Answer by: Bulk Reef Supply on Apr 14, 2014 12:21:00 AM
What is the output size on this pump?
Question by: Jacob on Mar 22, 2014 5:29:00 AM
Hi Jacob,
The output size of the pump is the same as 1/2" polyethylene tubing like those used with our reactors (which is a slightly different standard then 1/2" PVC). A 1/2" push connect union for example will snap right on.
Answer by: Bulk Reef Supply on Mar 22, 2014 5:29:00 AM
If you're using this pump as part of your ATO system, what is the size of the output? I'm getting the Hydor ATO system and this pump was recommended by you. I would like to get the correct size tubing before I get the pump and set up the system. Thanks.
Question by: David on Apr 5, 2014 4:52:00 PM
Hi David,
The MJ1200 has an output that is actually the same size as 1/2" RO tubing, so conveniently you can actually use a 1/2" push connect union on the end to connect the pump to 1/2" ro tubing just like we do with our BRS reactors.
Answer by: Bulk Reef Supply on Apr 5, 2014 4:52:00 PM