Mastering Freshwater Aquarium Ecosystems
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Filtration (Cont.)

UG filters usually work quite well for the first 4 to 6 months, but they can become problematic in aquariums that have been setup for a long time. Detritus will build up under the filter plate and cannot be removed with vacuuming. Usually, you will have to take down the entire aquarium to clean out this detritus. Taking down an entire aquarium is not something I recommend if you plan on restocking with the same fish as you may end up going through establishing a nitrogen cycle again.

Some hobbyist have used UG filters in a reverse flow configuration. With a reverse flow, the water is pre-filtered and forced under the plate, allowing water to come up through the substrate. This configuration will still build up detritus over time, just not as fast as the typical configuration.

Large cichlids that like to dig and move substrate around are a poor choice for aquariums that have a UG filtration system. When the gravel is not even across the bottom, water will follow the path a least resistance. This can cause dead spots in the UG filtration system and affect the efficiency of the filtration.

Because of the water quality issues that can develop with UG filters, they are my last choice when choosing a filtration system for an aquarium.

Box Filter

Lee's Large Corner Filter

Lee's corner box filter. Photo from Lee's.

Box filters are air driven filters that are normally placed in a corner. They can contain chemical filtration media, biological media, and polyester fiber for particulate filtration. Some hobbyist use box filters in breeding tanks, as their gentle filtration will normally be fry safe. Box filters are easy to clean, and multiple filters can be powered by a single air pump.

Sponge Filter

ATI's Hydro Sponge

ATI's Hydro Sponge. Photo from Doctors Foster and Smith.

The most common sponge filters have an uplift tube that has a sponge attached to the end that collects floating detritus. They provide a lot of surface area for beneficial bacteria to colonize. Sponge filters are used most commonly in small aquariums, and bare bottom fish breeding tanks. Sponge filters come in many sizes and shapes. Sponge filters are most commonly air driven, but some aquarium product manufacturers do make power driven sponge filters.

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