External Filters sumps pros and cons

External Filters Sumps Pros and Cons

External filters, sumps are usually located under the aquarium inside the cabinet.

Long considered the King of filters, external filters have in recent years lost some ground to some types of canisters, despite its drawbacks such as difficulties set up, more budget, etc, while they are powerful, highly efficient and have a high retention capacity, external filters are still a major player in tanks over 120 L.

Let’s see some pros and cons of external filters sumps:

External filter sump

As external filters sumps are larger than internal filters. They have more filter media inside which results in less frequent cleansing than internal filters and are more versatile with various specialist filter media available to improve the water quality and keep fish healthy.

External filters are usually more expensive than internal filters but will be worth paying the extra money for versatility and greater filtering capacity.

External filters sumps usually fit into the cabinet under the aquarium connected by two tubes. Water is pumped from one end of the aquarium, filtered and then returned back to the other end of the aquarium via a spray bar or other spray nozzles.

Mountain Tree sump for aquarium

Filtering the water in an external filter is achieved through various chambers. The first is the coarse mechanical cleaning which removes the larger particles, fish manure, and waste fish food,  the second is biological which cleans the water of harmful ammonia, nitrate and nitrite and the third is the polishing which removes the very fine particles. Finally, there is the UV sterilizing, which kills all pathogenic leads to fish diseases from the water.


As the external filter has a big filtering capacity, the chambers of the filter can be easily adjusted to suit the tank conditions, for example, a larger coarse section for large messy fish like goldfish or specialist media such as Mountain Tree Filter Brush to greatly improve your water condition.


Many of the new external filters now have a self-priming mechanism which allows water to be drawn from the aquarium into the filter ready to be pumped back into the aquarium. This device makes life easier when cleaning or servicing the filter.


External systems sumps do have some disadvantages: set up is a bit more technical with suction and discharge tubes going outside the tank, manual start-up is a bit trickier, and a more substantial budget is required.


Many hobbyists reckon external filter especially bottom filter very difficult to set up and maintain. That’s because they might have chosen the wrong filter media to apply. It is recommended to choose high efficiency, convenient and carefree filter media.



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