Cobalt Aquatics EXT Canister Filter Review

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While a fish (or multiple) is not the most high-maintenance of pets, taking care of their environment and the aquarium you have them in does take a little bit of work.

Finding the right filter to help keep the water clean is part of that maintenance. The Cobalt Aquatics EXT Canister Filter is one of the many options on the market that will help you do just that.

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The EXT filter works on a variety of aquariums, terrariums, and vivariums; is super quiet and self-priming.

While there have been some complaints of leaks, some of the parts being cheaply made, and it becoming clogged quickly, let’s take a closer look and then you can decide if this is the filter for you and your fish.

Cobalt Aquatics EXT Canister Filter: The Details


  • Weight: 6 lbs.
  • Dimensions: 8 x 8 x 12.8 inches
  • Filter Capacity: up to 55 gallons
  • Flow Rate: 210 gph (800l)max.
  • Media Stages: Mechanical, Biological, and Chemical
  • Self-Priming or Standard: Self-Priming
  • Warranty: Three-year warranty


Filtration Stages

The EXT filter includes four stages of filtration: mechanical, chemical, biological, and polishing.

The first stage involves a filter sponge taking out the big, floating pieces of debris and particles from the water.

This stage also includes some biological filtration, but it’s only as an extra to the full biological filtration that will happen at a later stage.

The second stage uses activated carbon to remove any heavy metals, discolorations, impurities, or smells from the aquarium water and system.

The third stage is when the full biological filtration occurs. Porous ceramic rings provide a surface for bacteria to combine and oxidize with nitrogen. This will help build up your aquariums natural biological filter, especially if this is a new tank.

If new, your fish haven’t had time to build up ammonia for the bacteria to thrive on. The bacteria is needed to create a balanced habitat. Any change or upset in this nitrogen cycle may show in the plants and the fish themselves.

The fourth and final stage of filtration is the polishing stage. This involves a fine filter floss which captures any leftover debris and particles.

This final process makes sure the first mechanical filtration didn’t miss anything.

Multiple Installation Methods

There are also three different ways you can install your Cobalt Aquatics EXT filter:


Install the intake pump inside the tank. Install the filter on the inside wall of your aquarium.

As the pump is inside the water, you don’t need to force the water to go to the filter.

This method is recommended for most types of fish tanks.


Install the intake pump outside of the tank and make sure it is lower than the aquarium water level.

This will be performing the function of a flow pump. However, if you choose this method, you will have to prime the pump and that means sucking the water into the intake hose to start the pumping.

Anyone who has done this knows it is not the most enjoyable process.


Install the intake pump inside and at the bottom of the tank. This will allow the pump to supply the filter with water directly.

This method is recommended more for aquariums that have lower water levels.


The Cobalt Aquatics EXT Canister Filter comes with:

  • An inline pump
  • 5/8-inch tubing,
  • Intake and return pipes with an intake Strainer and a return spout/deflector
  • Elbow fitting
  • Suction cups

The filter also comes loaded with filter media for a quick and easy setup.

*Cobalt Aquatics does recommend you install a pre-filter in the form of a sponge cartridge or filter on the intake strainer, but this is not included.



Maintenance on an aquarium can be hard enough, not to mention cleaning out a complicated filter. Cobalt Aquatics tries to make it as easy as possible.

The EXT filter includes a quick-release valve that is for when you need to do maintenance on your filter. When the valve is turned to the far-left position, it disengages from the canister, creating a closed loop for the water.

The water will be directed back into the aquarium, allowing you to disconnect the cannister to complete maintenance without stopping the water circulation that is so necessary for an aquarium to function properly.

The intake pump also needs regular cleaning of the impeller. You are going to want to remove any and all of the impurities from the impeller chamber.

To perform this action, disconnect the device from the power outlet. Twist the pump cover counterclockwise until it comes off and then you can remove the impeller cover.

Then, after removing the impeller, clean it with the impeller chamber. All you need is a soft brush.

In the case of the pump operating outside of the tank as a flow pump, it is recommended to regularly maintain the gasket placed under the impeller cover by cleaning it and lubricating it thoroughly.

Make sure you use an aquarium-safe lubricant.

Filtration cartridges inside the filter should also be regularly washed in water that is removed from the aquarium (not regular tap water).

The first cleaning should be performed after two months from when you first started using the filter. After that, just look out for a decrease in efficiency and then you know to clean it again.

For the filter to do its bests job, you will also want to replace the cartridges at least once a year.

Side note: Use multiple Cobalt Aquatics E-X-T Canister Filters to suit the filtration needs of larger setups.

Cobalt Aquatics EXT Canister Filter Review

The Positives

Super Quiet

You’ll be impressed with how quiet the EXT Canister Filter is. This is a pretty big deal considering filters in the past could be very noisy.

Having aquatic friends always adds a bit of beauty to a room, but the noise coming from a tank can quickly become an annoying feature – especially for those with sensitive ears.

If you have more than one aquarium, these filters will be a dream for you; no extra noise whatsoever so you won’t have to battle with the sounds coming from your filter.

Less Expensive

At its price point, the EXT filter is much less expensive than filters that do similar things.

cobalt aquatics ext canister filter review

Especially if you are looking for more than one, a higher price could set you back hundreds (if not thousands, depending on how many tanks you have).

Spending a lot of money on materials and products can really be deterring for those looking to get into the hobby. Fortunately, the EXT provides you with a more affordable option.

Easy Maintenance

Maintaining and cleaning your tank is a groaning task that not many look forward to, especially if the process is complicated and fussy.

Not only can you continue water circulation while you disconnect the canister for maintenance due to the quick release valve, but the filter also comes with easy to open and close clips as well as removable media trays.

This makes cleaning and maintaining your filter’s efficiency so much easier. Cue sighs of relief.

Large Media Trays

And speaking of… the EXT filter has extra-large media trays to catch all the impurities in the water.

You are less likely to have the filters miss something, so more of the stuff you don’t want in your fish’s environment is filtered out – even the small stuff!

This also makes it easier to clean.


Warranties are a godsend when you’re just not sure how a product will work for you. It’s always nice to know the company has your back should anything go awry.

With the Cobalt Aquatics Canister Filter you’ll be given a 3-year warranty should you notice any errors or flaws in craftsmanship and manufacturing.

The company promises to repair or replace your product should an error be found. Simply contact their customer service department and they’ll give you instructions on how to move forward.

Note that the pump impeller, filter media, and shipping costs are not covered under this warranty.

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The Negatives

Pump Leaks

One problem our testers encountered was a leaky pump. It didn’t matter as much when the pump was installed inside the tank, but when installed on the outside, water would get everywhere.

And if a product is working correctly, it should not make more mess for the user. If you’re aiming to install this filter outside of the tank, be wary of leakage.

Cheaply Made

Multiple users also commented on how the tubing, the pump, and the multiple accessories this product comes with appeared to be very cheaply made.

There were also complaints that the filter didn’t come with any clips or clamps to secure the intake and outflow hoses, meaning they were loose and sliding around.

Instructions Too Small to Read

A lot of users talked about the instructions being either too small to read or that they didn’t make sense, so you’ll be left to visit YouTube and find tutorial videos that are much more helpful.

While it’s great that there is a place where users can get the instructions, Cobalt Aquatics should be providing usable ones as well.

Here’s a video showing how to set up the Cobalt Aquatics EXT Filter.

Overall Verdict

After going over all the positives and negatives, we are cautiously recommending the Cobalt Aquatics EXT canister filter.

The fact that it’s quiet, easy to take care of, and has large media trays cannot be overlooked.

Those are great qualities. But just be aware that some users have had issues with the instructions, the pump leaking, and the hoses and tubing looking cheaply made.

In the end, it’s your decision. Is the EXT the canister filter for you?

Where to Buy the Cobalt Aquatics EXT Canister Filter

Filters are often necessary for making sure that your tank is clean, and your pets are happy. And when it comes to choosing tools for your pets, Cobalt Aquatics offer a number of products like the EXT Filter.

While it’s always best to check pet stores and specialty shops, it won’t be too hard to find the Cobalt Aquatics EXT Canister Filter both in-store and online.

To start your search, check out the following online retailers.

And of course, you can also find this canister filter on Amazon.

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That’s all for our Cobalt Aquatics EXT Canister Filter review. Willing to give it a try?

Cobalt Aquatics EXT Canister Filter Rated
  • Quality of Filtration
  • Build Quality
  • Accessories
  • Ease of Use
  • Value for Money

FCG Verdict

This external canister filter may have its flaws, but its quiet, easy to use, a breeze to clean, and its large media trays cannot be overlooked.

The price may be a deterrent and the instructions confusing, but it still leaves you with a product that does its job.

>>> Check current price on Amazon.

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