Wet Dry Aquarium Filters

Busy Wet DryOne of the best choices for an aquarium filter whether your tank is a freshwater aquarium or especially a saltwater or reef tank is the wet dry aquarium filter.  Filtration systems like internal filters and canister filters do a good job on freshwater tanks and an adequate job on saltwater tanks that aren’t too large with fish only.  The top pick of the vast majority of saltwater aquarium owners is the wet dry aquarium filter. The majority of manufacturers and retailers will have guidelines as to what will work best for your size tank.

The wet dry filter is typically located below the tank in the tank stand or aquarium cabinet.  Water flows from the aquarium, either from an internal prefilter box or a natural gravity flow or even a pump driven source, down to the wet dry filter and is distributed across any number of media.  The majority of the water from the aquarium is surface skimmed in order to remove most free-floating particles from the tank.  This also provides a clean water surface. The water in the filter is evenly spread out across the media via a drip tray or a rotating pipe “sprinkler effect”.  This trickling of water across the media in the filter is why a wet dry filter is also referred to as a “trickle” filter.

Once the water reaches the media, which is higher than the water level in the filter or sump, it is returned back to the tank by a pump.  cpr wetdryThe reason the media is actually higher than the water level in the filter is so that the bacterium on the bioballs, biocubes, or biobale, etc can develop to efficiently and effectively remove both ammonia and nitrites from the water.  This is also how the name wet dry filter came about.  It appears that the media above the water level is in a “dry” area of the filter when in reality it has water constantly trickling over it.  In the sump area where the return pump is located the aquarist will usually place any carbon filtration, dosing pumps or a heater.  By placing these items as well as other filtration options in the sump area, it gives the tank itself a nice clean look without wires or cords.

The above description is true for both freshwater and saltwater aquariums that utilize a wet dry filter.  However, in saltwater environments, the use of protein skimmers, also known as foam fractionators, and calcium reactors, refugiums, chillers, and similar options may be placed in the sump filtration area.  Many hobbyists and professionals will add an extra sump area with bulkhead fittings in order to accommodate the extra items that they wish to place in their setup. While the necessity of changing or replacing your carbon and various filter resins may be required monthly or biyearly, the majority of the trickle filter media may only need cleaning once per year or less.

Once the wet dry filter is up and running, the main concern should be targeted on the flow of water.  If the pump cannot return the Wet dry illustrationfiltered water back to the tank quick enough, the sump will overflow and water will be on the floor.  Conversely, if the pump is returning the water too rapidly, the sump will drain and you might end up with water coming out of the tank itself as well as your pump sucking air and possibly burning out.  A valve should be placed after the pump; never restrict a pump between the pump and the filter…it can cause the pump to work too hard to get the water it needs to operate correctly.  The valve will allow the aquarist to easily adjust the flow so that the amount of water returned to the tank is the same as the water coming from the tank.  The other concern that might require regular attention is to replace or clean prefilter materials so that it doesn’t clog and restrict the overall flow.

I hope that this article helps to explain some of the details that are required when using a wet dry aquarium filter.  It isn’t rocket science, but if it is set up incorrectly or if it is ignored for too long, the cleanup of water on the floor and the potential for electrical shock from water in the cabinet or tank stand can be extensive.

Wet Dry Aquarium Filters
Article Name
Wet Dry Aquarium Filters
A brief overall introduction to wet dry aquarium filters.

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