The aquarium filter you choose for your goldfish depend a lot on the size of your setup, and how much maintenance you want to do.
The purpose of a filter is not to make the water clean and clear. That is only a secondary benefit.
A filter’s primary purpose is to process the waste generated in the aquarium.
Over time, large numbers of useful bacteria colonize the filter media and process the waste from the water. This is called the nitrogen cycle, and all new aquariums must go through it.
Until these bacteria colonize the filter in sufficient numbers, any ammonia from waste will pollute the water.
Fish are very sensitive to ammonia levels.
Go to the page on setting up an aquarium to read more about the nitrogen cycle and how to test for it.
Having established that an aquarium filter is an essential piece of equipment that reduces the amount of maintenance you need to do, and provides some level of protection against mishaps, the decision now is to decide which one best suits your setup.
Goldfish are messy bottom feeders, producing a lot of waste. Some filters are more efficient than others, so you need to choose the correct filter to avoid having to clean it out every two weeks.
An aquarium filter well suited to a setup shouldn’t need cleaning out more than three or four times a year.
As a general rule, the water should be turned over at least four times per hour. Most power filters will give a gallons or liters per hour figure. This figure will be for a new filter that is unclogged. Always go bigger with a filter rather than smaller to allow for efficiency to drop over time as the filter gets clogged.
You can never over filter an aquarium but you can certainly under filter one.
There is basically two ways filters move water:
Filters that have electrically powered water pumps generally move far more water than do air powered filters.
These filters sit outside the aquarium. Most canister filters have an integrated water pump that sits on top of the canister body, but larger very high capacity types can have the water pump situated away from the canister and connected by hoses.
They have three or more trays or compartments for filter media.
These filters hang from the side of the aquarium, usually the back. They have a small pump that sucks up water from the aquarium where it goes through a series of chambers before returning to the aquarium.
These filters sit underneath the aquarium gravel.
They usually use air bubbles to move the water, but in bigger installations power heads (water pumps) are used.
They work by pumping air down a small tube into the base of a larger tube. The air returns to the surface as bubbles. This action draws water up the larger tube. The water has to pass through the gravel before it returns to the aquarium. The gravel is used as the filtering medium.
Note: Bigger installations that use power heads pump the water down the tubes forcing the water underneath the gravel.
These filters use air bubbles to move the water, similar to under gravel filters. The filter media is usually sponge material. They are used mainly in smaller aquariums.
These filters are similar to the internal box filter but don’t have a plastic body. They either sit on the bottom or can be attached to the aquarium side with rubber suckers. Sponge material fits around a perforated tube. Air bubbles are released at the base of the tube and as they flow upwards to the surface, they drag water through the sponge material.
These filters are often used for fry aquariums as the fry can’t get sucked into the filter body.
These filters sit on the bottom or attach to the side of the aquarium using rubber suckers. Most use sponge material as the filter media.
These filters are becoming more popular in larger setups, and usually come with the aquarium. A power head pumps water up into a tray or trays that sit on top of the aquarium, usually under the cover.
The tray is divided into sections that can have different filter media in each, similar to a canister filter.
There are a few other specialist filters such as wet/dry filters and protein skimmers, but these are for sophisticated setups and aren’t required for the majority of aquariums.
If you need an aquarium filter, Amazon.com have a wide selection at competitive prices.
If you want a quality product that will last, and have spares available, choose one of the well known brands such as Eheim and Fluval. Yes they are more expensive, but some of the Asian sourced products I have tested start showing pump rotor wear after just six months.
If you decide to purchase one of the cheaper external canister brands, check the groove where the sealing ring sits very carefully. I have found poor finishing often leaves small amounts of material in or around the groove stopping the sealing ring seating correctly leading to leaking.
I would strongly advise testing a cheaper filter first so if it leaks it won't do any damage to flooring or furniture.
When your aquarium filter needs cleaning, there is a set procedure to follow otherwise you will destroy all the useful bacteria that are living in the filter. To learn how and when to clean aquarium filters correctly go to this page…
To learn about what filter media you should use and where to place it in your filter click here...