LiveAquaria Approved Aquatic Supplies: Cobalt International MJ Multi-Purpose Powerhead Pump
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Cobalt International MJ Multi-Purpose Powerhead Pump
Cobalt International MJ Multi-Purpose Powerhead Pump
Additional locales and sizes may be available!

Please Note: Return of electrical equipment to LiveAquaria for exchange or refund is limited to 30 days from the date of purchase. Beyond 30 days, please contact the manufacturer for repair or replacement as covered by the manufacturer's warranty.

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* Made in Italy for superior performance as powerhead or pump
* Built to perform reliably even under the harshest aquarium conditions
* Use as powerhead, wavemaker, or as protein skimmer calcium reactor or refugium pump

The ORIGINAL workhorse built to perform AND last! Cobalt International MJ multiuse submersible pump and powerhead brings back the superior Italian-made performance you've trusted and relied on in the past. Energy efficiency, versatile internal or external use in freshwater or saltwater marine aquariums PLUS easy-to-reconfigure design makes this multitasking pump great for tackling all your aquarium needs - even under the harshest aquarium conditions!

Cobalt International MJ Multi-Purpose Powerhead Pump is great for use with wave makers, protein skimmers, calcium reactors, nano aquariums, undergravel filters and any application where reliable water movement or circulation is essential.


  • 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
  • 1/2" outlet in return pump mode

Model Max
MJ-900 230 46" 8.5
MJ-1200 295 69" 20

Install the Venturi device and Flow Deflector. Position the pump with its Conical Adapter on the lift tube of your undergravel filter. The powerhead must be at least partially submerged but may also be used fully submerged. Normally the specially designed Lift Tube Adapter will keep your powerhead in the position you have chosen. If additional stability is necessary, utilize the Suction Cups or Mounting Hook.

  1. To use a Suction Cup, press it into the Mounting Bracket and slide the Bracket into one of the three Mounting Grooves on the pump body. Press Suction Cup to side of aquarium on a smooth, clean surface.
  2. To use the Mounting Hook, slide it through Mounting Bracket. Press a Suction Cup into base of Mounting Hook and then mount on pump by sliding Mounting Bracket into one of the three Mounting Grooves on the pump body. Position pump in aquarium by snapping hook end over the top frame and pressing Suction Cup to glass to secure firmly. Adjust position of the pump, up or down, by sliding Mounting Bracket along the Hook. A small clamp is supplied to guide power cord and airline tubing. Press the clamp on top of the clamp as desired. Note: Suction Cups and Mounting Hook can be used separately or together.

Use of Aeration Feature
To improve aeration and gas exchange, the Venturi Aeration Feature may be utilized together with the airline tubing and air filter supplied with your pump. Two small red Air Tubing Adapters are supplied for any size of tubing. The Air Filter also functions as a valve. When using the Venturi air-mixing feature, air volume can be adjusted by turning the top part of the Air Filter. Note: Aeration decreases if water volume is low or if pump is positioned too far below the water surface. Water volume decreases when the Venturi feature is used.

For optimum performance, it is best to periodically clean the internal moving parts with warm water. If the Rotor becomes encrusted with lime scale, use vinegar or lemon juice to remove buildup. Do not use solvents.

When using your MJ pump with calcium reactors it imperative to perform monthly maintenance to remove buildup of calcium residue inside your MJ pump.

  • Unplug and remove the MJ pump from the water
  • Remove the impeller
  • Pour vinegar into the impeller housing well inside the motor
  • Soak the impeller housing and impeller overnight
  • Brush the impeller and impeller well with a toothbrush removing deposits

Troubleshooting Guide

If the impeller is not turning. . .

  • Unplug and remove the MJ pump from water
  • Remove the impeller
  • Plug the MJ pump in
  • Run the impeller around the outside of the casing. If you feel magnetic motion then your MJ pump is good (99% of the time it's fine).
  • If it has no motion then, please contact the manufacturer for replacement (motor is dead).

Please Note: If the impeller does have motion then the MJ pump is fine but may need an impeller replacement.

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