Q. Do I need a wet/dry filter?
A. A wet dry filter is a device that provides an area or surface for bacteria to colonize, upon which water is distributed in a manner that allows air to reach the same surface. The theory is that the bacteria need oxygen in order to process the waste. This is also referred to as aerobic activity. Wet dry filters are typically an acrylic box(sump) that water from the tank pours into, passing over the media (typically plastic bio-balls) and then through an open area where a sponge, carbon, and or a protein skimmer is placed and then pumped back to the tank. There are also models that hang on the back of a tank.

Essentially a wet dry filter serves primarily as the biological filter. It may also provide for mechanical and chemical filtration components.

We recommend a wet dry filter only in circumstances where it is not possible to utilize live rock as the biological filter.

Wet dry filters are extremely efficient at converting ammonia into nitrate. They often necessitate frequent and large water changes to counter the increasing levels of nitrate.

A significant flaw in the use of wet dry filtration is discovered in the event of a lengthy power outage or if the main circulation pump should fail. The tank is then a sterile environment with no filtration (biological) at all during this period. Furthermore the non-oxygenated water in the filter area will often suffocate and kill the bacteria. When power is restored and or the pump repaired your tank full of expensive and delicate fish will suffer or die due to the lack of biological filter. While the biological ability of the filter will eventually restore itself, it may take too much time.