Advantages and disadvantages of external vs submersible aquarium pumps - Continued

Continued from page one - The filtration medium itself can be varied within the canister, and they are very flexible in allowing a combination of mechanical, biological and chemical filtration systems. Since they are external, it is easier to change the medium to specific types and also make adjustments to the electrolytic properties of the water to suit specific fish type. An additional benefit is their ease of cleaning external to the tank without disturbing the fish. Not that they need frequent cleaning: a clean-out every 2 – 3 months is generally sufficient.

However, all is not completely rosy in the external pump garden, and there are one or two disadvantages in comparison with the submersibles. Their price for starters: they are expensive when compared to the submersibles, and are not always simple to install compared to the relatively easy submersibles. Other than that, however, and the need to find storage space outside the aquarium for it, there are very few negatives.

It is also pretty simple to choose a model suitable for your needs. However, they are not suitable for all aquariums, since they have a lower volume limit. They are not suitable for anything of a capacity less than 75 liters for which a submersible would be the better choice. Like any other pump, it should be capable of a total water change every 2 – 6 hours depending on the density of fish and the most suitable water conditions for the fish that you stock. If you are unsure what you need then go for the average figure of four hours.

You can calculate that from the pumping rate of your pump and the capacity of your tank. A 200 liter tank requires an average pumping speed of 200 liters every four hours, or around 0.8 liters a minute. That is the rate for the complete filtration system.

The benefits of external aquarium pumps are many over their submersible counterparts, but they are expensive and you must weigh up these benefits against the extra cost. For the enthusiastic amateur they are probably worth the expense. Someone just starting out should probably hold back on the expense until they are confident that this hobby is right for them.

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