Cobalt MJ1200 Powerhead Review

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Size Dimensions Tank Size Noise Level Longevity Max Height/Head
295 GPH 6″ x 3″ x 2″ 15-40 Gallons Very Low 7+ Years 69″

The Cobalt MJ1200 is the revival of the older Maxi-jet powerhead. Unlike the newer Maxi-jets, which have been downgraded to cheaper materials and production in China, the Cobalt MJ1200 still uses metal for many of its components and is produced in Italy, ensuring a much longer lifetime.
short description better design than cheaper Chinese model. uses metal on sensitive parts instead of plastic to ensure no short lived pumps.


Putting the MJ1200 into the tank is a quick and easy process. First you will need to decide between the suction cups or hanging bracket mount. The suction cups will hold the powerhead in place quite nicely and prevent any vibrations against the glass of the tank. As for the hanging mount I am not sure why it would be used. It often creates much more noise and is more susceptible to running dry after water has evaporated. Still it does keep the powerhead in place and near the surface of the water.

For the suction cups you will need to press all three into place on the u shaped mounting bracket. Next you will slide this bracket onto one of the groves on the back of the powerhead, connecting the two together. The hanging bracket is also connected the same way.

With the mounting device in place you can either stick the suction cups to the glass or hang the bracket on the rim of the tank.

The cord is 6 feet long giving you more than enough to place this powerhead anywhere you want. I actually left a lot of mine coiled up, as it was too much cord for my needs.


The Cobalt MJ1200 comes equipped with an impeller rather than a propeller. This provides less water flow but removes several issues that propellers often have.

The impeller does not create any noise when started and cannot run in reverse. This is essential for water pumping powerheads, as any reverse running could easily cause hundreds of dollars in damages.

The impeller runs at an almost silent level, getting even quieter when deeply submerged in the tank. The only thing I’ve found that can increase the noise is the tubing when using this as a water pump. Too tight of tubing, smaller than 1/2 ID which is the normal accepted size for this model, will create too much back pressure and make the impeller rattle against the sides.

The small impeller design and attachable grates are next to impossible for fish to enter. Only fry and feeder shrimp such as brine would be able to enter the grate. The output is fairly small and does not lead directly to the impeller blades, ensuring no fish can enter this way either.

The small hook at the top of the motor can hold in place an airline tube. This can be connected to the powerheads output to inject air into your tank. This is an absolutely fantastic feature for freshwater tanks, as the powerhead will replace any air pumps the tank may have. Not only is that less equipment running, but the air pump is always one of the loudest parts of any freshwater tank.


The MJ1200 is designed for its parts to be used interchangeably, making it easy to disassemble and reassemble at any time. All parts will simply come apart with minimal puling force, but are still resistant enough to hold together under water. I’m not saying it’s cheaply held together, the parts just slide off if you pull on them.

For cleaning you will want to remove the motor from the nozzle and grate, which will expose the impeller. This can also be removed, allowing you to clean out the impellers housing. Keep in mind that the impeller uses a magnetic base to spin and must be cleaned off with care. Use soft materials such as a cotton swab, as any scratches will cause irregular spinning and damage the impeller.

Note: For those who plan on using this in reef aquariums, the pump is susceptible to calcium build up. To remove this you will need to soak the powerhead in distilled vinegar for up to 20 minutes every 2-3 months, rinsing it off before returning it to the tank. Calcium caused damages are not covered by the warranty.

Flow & Adjustments

The Direction of the MJ1200 can be directed any way you choose with the use of the venturi adapter. This is the vacuum shaped adapter and spins in to face any direction.

The speed itself is not adjustable but the flow can be diffused by directing the flow towards the side of the tank. This spreads out the flow and makes it much more gentle. You will need to do this if you are housing betta fish, even in large tanks.

Warranty & Lifetime

Cobalt provides a 3 year limited warranty, which covers any damages caused by poor construction. This does not cover any human caused damages, except for shipping, and also does not cover calcium build up. Why they target calcium so specifically is beyond me, as lime and magnesium can cause the same issues. Still be sure to follow the cleaning process mentioned in the assembly section to prevent this damage. To contact their support simply call their support line at 803-591-9500.

The lifetime is where the better design and higher cost materials come into play. The MJ1200 powerhead will almost always live past 7 years, with most users seeing 10 or more years of lifetime. This makes the Cobalt MJ series one of the most cost efficient powerhead/water pumps out there when it’s well cared for.

Extra Note: The MJ1200 comes with a self resetting thermal protector that shuts off the powerhead when it runs dry or has a jammed rotor. This will keep the powerhead from heating up the water or damaging itself. To restart the powerhead you will need to fix whatever blocked the impeller and keep the powerhead unplugged for at least 1 hour. After that the thermal protector will reset and the powerhead can be used normally.

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