Aquarium Hang On the Back Power Filters (hob Filters), Their Strengths and Weaknesses (especially in Bio Filtration)

HOB filters (hang on the back- power filters) are quite popular for good reason. They are generally inexpensive and simple to operate. But they do have a couple of weaknesses, especially in bio filtration and in the case of Aqua Clears: a high "flow by rate".

[1] Bio filtration; The Aqua clear is better here than others, but it has a weak impeller design that is not very durable and they are prone to leaks. The Aqua Clear is also a poor mechanical filter with a high "flow by rate" (the amount of water that actually is forced thru the filter media).

That leaves the cartridge models starting with the Penguin. The Penguin has a much lower "flow by rate" than the Aqua Clear and is less prone to leaks, but their bio filtration is poor, even with the bio wheel, which is vastly over-rated in my tests I preformed through my aquarium maintenance business. I removed the bio wheel on penguin filters on comparable aquariums with comparable bio loads and fish and found no discernable ammonia spike. Yet when HOB filters that had running pre filters attached to their intakes were removed, there were discernable ammonia spikes.

The Whisper and ReSun the HOB filters I prefer the most. Both these filters have a low "flow by rate". The ReSun is a much better value and is less prone to leaks, but the ReSun currently has a poor choice of filter size options.

This brings me to the point that ALL HOB filters should be equipped with Pre Filters (the Filter Max is the best due to its patented sponge technology). Pre Filters vastly increase bio filtration, are inexpensive ($4.99 and up), prevent baby fish from being sucked into the filter, and provide a measure of bio stability when the cartridge is changed.

[2] The other weakness of HOB filters is the poor cross circulation they provide (HOB filters provide vertical circulation). Cross circulation is especially important in larger aquariums such as a 48" 60 gallon aquarium. For small aquariums such as 20 gallons or less, this is of less concern, although I would still consider an addition filter such as an air driven sponge filter for redundancy.

This is easily remedied with an Internal Filter. I recommend the Via Aqua Internal Filter due to its reliability, and inexpensive sponge media which keeps it simple to keep.

For more information about sponge filtration, please see this article: "Sponge filtration"

Tagged as: Aquariums, Hob, Low Flow