Sponge or Breeder Filters
Filtering Your Aquarium Water
(The First Tank Guide)
What Is a Sponge Filter?
Sponge filters are any aquarium filters where the aquarium water is drawn through a sponge mounted or sitting inside the fish tank. Most of the time, these filters have a replaceable sponge and are powered by an external air pump.
The sponge itself mounts to a core which, in turn, mounts to a lift tube and air line or a water pump. The sponge may rest on the bottom of the tank, in which case you can put it on, in, or under the gravel. Other models will mount to the side of the tank and should be placed as close to the bottom as they will fit to provide optimal water circulation.
How Does a Sponge Filter Work?
A sponge filter uses bubbles of air from an external air pump, or an integral water pump to draw water through the sponge. As water is drawn out through the lift tube or pump, it is replaced by water entering the sponge. The sponge is a mechanical filter and the surface of all the bubbles or pockets in the sponge provide a bed for the bacteria of a biological filter. Sponge filters provide both mechanical and biological filtration.
What Maintenance Does a Sponge Filter Require?
The sponge will need to be rinsed or replaced every time it becomes dirty, about once every 1 to 4 weeks, depending on tank load, kind of fish, feeding schedule, type of food, cleaning schedule, and what other filtration is available and in use on the fish tank. Some sponge filters have small carbon cartridges which need to be replaced regularly - and frequently, possibly as often as daily - or can be left off entirely. Remember that carbon cartridges that become saturated with waste chemicals could potentially release other toxins into your tank.
What Should I Be Aware Of with Sponge Filters?
Most sponge filters are reasonably efficient filters for small volume tanks. These filters, especially the air driven ones, are excellent for hatcheries, maternity tanks, nursery tanks, and fry tanks, as the filter produces minimal current and has almost no way to suck the fry through the filter.
As the filter ages, the sponge will begin to deteriorate. When this happens, it is important to replace the sponge with a new one. Though these sponges may last several years or more, when they are replaced, remember you are replacing your entire biological filter unless there is another filter on the aquarium. When the biological filter is replaced, the tank will go through the cycling process again.
If you have a sponge filter in a display tank, you should consider getting a second filter so that you do not remove all of your bacteria bed every time you replace the filter sponge. Having the aquarium cycle again can be fatal to your fish due to 'new tank syndrome' and ammonia poisoning.
Remember to remove any carbon from the tank or filter before you medicate (if the carbon is working, it should remove the medication from the tank in under an hour, in which case your fish won't get treated).
Why Are Sponge Filters Sometimes Called Breeder Filters?
As mentioned at the top of the page, sponge filters are sometimes, or often, depending on which circles you are operating in and who you are listening to, referred to as breeder filters.
This is because one of the primary uses of sponge filters is by breeders in their fry tanks or nursery tanks.
These filters are used in many fish breeding operations because the filter has no way for try to get sucked into the filter and trapped or injured.
Breeders also use these filters in their rearing tanks because, short of the under gravel filter, there isn't a lower maintenance filter. And sponge filters have the advantage of being fully functional in an otherwise completely bare tank.
Because these filters can be used in completely bare tanks, sponge filters are also used by a number of fish distributors and wholesalers, where being able to quickly catch large numbers of fish is important, and where it is also important to be able to quickly see whether a tank is empty or not.