Sponge filters have been around almost since aquarium-keeping began. However, many aquarium owners either have no idea what they are used for or don't know they exist at all. Although sponge filters aren't suitable for every tank, there are situations in which they are perfect.
What Are Sponge Filters?
Sponge filters are precisely what the name implies, a sponge through which the aquarium water is drawn. This provides mechanical filtration, and once the sponge has matured and grown bacterial colonies, it provides biological filtration as well. Sponges come in a variety of shapes and sizes, as well as pore sizes. This allows them to be adapted to a variety of filtration needs. They can be powered by a number of methods, including air pumps, powerheads, or even another type of filter.
Using Sponge Filters for Gentle Filtration
Sponge filters are excellent when safe and gentle filtration is needed, such as in a fry tank where young fish could be sucked into the intake of standard filters. Fish species such as bettas that do not thrive in strong currents also benefit from sponge filters. Shrimp are another species that requires very gentle filtration rather than a strong intake that would suck them in. Sponge filters are also great for hospital tanks, where fish are often weak and not able to tolerate the stronger suction from a standard filter inlet.
Sponge Filters for a New Aquarium
Another use for sponge filters is to jump-start a new aquarium. A sponge filter can be run on a well-established aquarium for several weeks or months to establish biological colonies. Once the new aquarium is set up, the matured sponge can be placed in a bag of water and transferred directly to the new tank, thus maintaining the biologicals. This gives the new tank an immediate biological boost, which in turn benefits the fish in the new aquarium by reducing the ammonia and nitrite spikes experienced in a new tank. Some aquarium owners keep a mall sponge filter running all the time in one or more of their main tanks, so they are prepared to set up a new aquarium or an emergency tank.
Sponge filters work well as a pre-filter on the inlet of a canister filter. The sponge filters out a good deal of the larger particulate matter, which keeps the canister from clogging. It is far easier to clean or replace the sponge pre-filter often, rather than tearing apart the canister filter. Additional biological filtration is also provided this way, and the sponge is ready for use in setting up an emergency aquarium should the need arise.
When using sponge filters either with an air pump, power head, canister or another filter, keep in mind that multiple sponges may be used. This not only provides additional biological and mechanical filtering ability but has the added benefit of allowing maintenance to be staggered so not all sponges are disturbed at the same time. It also gives the owner an extra sponge or two to seed a new tank with, if desired.
Downsides of Sponge Filters
The biggest negative when using sponge filters is the complete lack of chemical filtration. Sponge filters have no means to include chemical media, which means they can only provide mechanical and biological filtration. Many experts believe that's not a negative, as they feel chemical filtration is not all that it's cracked up to be. Certainly, an aquarium that has robust mechanical and biological filtration has minimal need for chemical filtration.
Another obvious negative with sponge filtration is the fact that they are not aesthetically appealing. Who wants a big old sponge detracting from the attractiveness of their aquarium? However, if the placement is well planned for when setting up the aquarium, the appearance can be minimized considerably. This is especially true in a well-planted aquarium, which can conceal most of the equipment, including a sponge filter.
Sponge Filter Maintenance
Sponge filters are relatively easy to maintain. The key is simply to remember to perform the maintenance regularly. The best way to clean a sponge is to perform a water change and save some of the water that was just removed. Submerge the sponge in the used aquarium water, then gently squeeze and release the sponge several times to dislodge particulate matter that has collected. If this is done every few weeks, the sponge will never clog completely and will last a long time.
Sponge filters are often used in multiples, either with two inlets or simply by stacking one sponge on top of another. If there are multiple sponges, stagger the cleaning schedule, so they are not all done at the same time. This will lessen the impact on the biological colonies, and minimize the potential for ammonia or nitrite spikes after cleaning.