Cobalt MJ900 Powerhead

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Cobalt MJ900 Powerhead

71% Recommend this to a friend (5 of 7)

SKU: 210502
In Stock: 42
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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: 230 GPH

  • Maximum Head Pressure: 46"

  • Power Usage: 8.5 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




7 Items

  • Good Value By Ronnie on 2/20/2015

    This powerhead/pump comes with several pieces and is interchangeable to fulfill all your needs. Quiet operation and powerful flow. Great product I would recommend this to anyone.
  • quiet pump By Theodore on 1/5/2014

    Much quieter than other maxi jet. Runs my gfo reactor with valve half open.
  • Quiet Pump By Brandon on 7/7/2013

    I bought this pump to replace my MJ1200 for my GFO/Carbon reactor. I like this pump better because it does the job and is quieter.
  • Better than Marineland By John on 3/13/2013

    I have only had this pump for 2 weeks, but there is no noise. I have had a MJ 900 from Marineland for 6 months on my GFO reactor and the noise was horrible. Now the only thing I hear is flow of the water from the output, no rattling.
  • 2 months later and it vibrates By Frank on 1/21/2013

    Perhaps I have a bad unit, but I've been running it for 2 months and it vibrates like mad. I added this pump to agitate the surface water and redirect my powerhead to the main tank. At first, the Cobalt was great, now (2 months later) it's vibrating horribly to the point that I will have to disconnect. Hopefully, a cleaning will take care of it, but if this is the case, then I would consider that to be ridiculous (I can go 6+ months on my other pumps and powerheads between cleaning). Either way, it's a big disappointment as it will not be easy to remove and I will likely have to come up with Plan C.
  • No Noise By Ron on 8/28/2012

    Great product. At first I bought a BRS reactor for carbon and with that I purchased a MaxiJet version of the same pump. I gave that a three star rating for excess noise. What I wrote then was: "I got this to use with the reactor instead of the recommended 1200 as it draws about 1/2 the watts with only a little loss in flow. The flow is fine and the price is fair, however the pump is loud to me. It is louder than my skimmer skimmer pump - skimmer is a reef octopus. On the plus it connects right up with the BRS reactors." This has the same pros but no noise cons. Also I use this on a second reactor with High Capcity GFO. Even this pump is overkill on pressure as I have to dial it way down to keep the tumbling just at the top and I have 1.5 cups of media in the reactor.
  • Cannot Loose By Carveth on 12/1/2011

    I've had tanks for decades. One item that has repeatedly proven itself is the original Maxi Jet powerheads from Italy. They are quiet and draw low amps so cool and inexpensive to run. The newer Maxi Jets are made in China. I have reef friends who say they do not work as well especially in back pressure situations. These Cobalt Aquatics are the same as the old tried and true original Maxi Jets. Buy these, the true Maxi Jets under a new name. The only problem you will have with these is they will never wear out and you'll have them forever.


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Product Questions

what size tubing does this require? 1/2 in id?
Question by: Lynne EZZELL on Jan 18, 2016 3:12:00 PM
Great question!
This can connect to 1/2" ID diameter tubing! Feel free to let us know if you have any further questions!
Answer by: Connor (Admin) on Jan 26, 2016 7:16:00 PM