Undergravel Filters (UGF)

The plastic grate in UGF lies under the tank’s gravel. Water flows freely under the gravel and is drawn through gravel, causing the mechanical and biological filtration. Power heads or air pumps will be required to move the water.

An air pump blows bubbles at the bottom of lift tubes and the power head pumps water out of the top of the lift tube and into the tank. The lift tube carries water when the bubbles lift water up. When moving out of the lift tube, the water is moved out and replaced with water from under the filter plate.

This pulls water through the gravel where the cleaning is done. Mechanical filtration is provided by the gravel. A bed for bacteria of a biological filter is provided by the gravel, the filter plate, tank bottom, and lift tubes.

Low maintenance is one of the key features of UGF. There is absolutely no need to change your filter media. The gravel though, does require regular cleaning. Use a gravel vacuum to accomplish this and clean a quarter of the gravel every time you need to go through your weekly water change. Failure to do this may cause the gravel to "channel." This is when the debris blocks some passages in gravel and forces water through channels. This in turn causes decreased water flow and exposure to water filtering bacteria is reduced. Other than that a UGF is low maintenance and incurs the lowest running costs. Using UGF for the first filter in a basic tank is highly recommended. To clean your UG filter you just need to siphon off accumulated gravel debris.

Advantages of Using an Undergravel Filter

Versatile: Undergravel filters are very multipurpose and can be used with Powerheads and other devices. Fluid-moving pumps can be costly and you can use air-lift systems instead to drive your undergravel filter. For more water flow you can use Powerheads to draw water through or push the water through UG plates. Even if you have no room for chemical filtrant, you can enclose Zeolite or carbons in porous filter bags. Just sweep a bit of the substrate to the side.

Invisible Filters: UG filters help in removal of detritus, uneaten food and excreta. They help convert this matter into liquids or gasses by biological and chemical methods. UG filters also provide a boost in added circulation through the substrate they offer. Of course bacteria can do forward reaction of nitrification and oxidation of ammonia to nitrite then nitrate using effective aerobic processes but use of UG filters makes this process far more efficient.

Easy To Use: UG filters are easy to install and operate and have no moving parts to worry about, no other gear to buy. All you need will be some airstones and an occasional pump diaphragm. This is literally nothing when you compare it with other filter types. Upkeep is relatively easy with no expensive, messy filter media required. Gravel and substrate are the only media and can be vacuumed for easy maintenance.

Easy To Use: UG filters are easy to install and operate and have no moving parts to worry about, no other gear to buy. All you need will be some airstones and an occasional pump diaphragm. This is literally nothing when you compare it with other filter types. Upkeep is relatively easy with no expensive, messy filter media required. Gravel and substrate are the only media and can be vacuumed for easy maintenance.

Inexpensive: Undergravel filters are cost effective in acquiring and operating. They are simple devices made with perforated grate raised up to allow water space underneath. Other types of filters can be complicated but UGF are very low cost, simple operations. They also have a longer and more useful life span.

Effective Filtration: Metabolite poisoning is toxic accumulation of animal wastes caused by overfeeding or livestock death which is rich in ammonia and nitrite. This toxicity in freshwater aquariums can cause captive aquatic life. In the presence of Undergravel filters though, this can be avoided. UGF can convert noxious wastes to less harmful substances. They are the best in eliminating increased metabolite presence. Undergravel filters enable rapid population with desirable microbial life and recover from challenges to your required bacterial organisms.

Disadvantages of Using an Undergravel Filter

Noxious Gases: Hydrogen Sulfide toxicity can cause fish and other aquatic living beings to die. This sometimes happens in aquaria with UGF which hasn’t been properly maintained. If you feed too much of inappropriate foods or neglect weekly maintenance and there is too much of bio load, then any of these neglected issues can cause production of noxious gases which can, in turn, cause dead zones. You will have to be attentive towards gravel vacuuming and water changing and other aquarium maintenance tasks.

Aquatic Plants: Floating or surface type plants are okay but rooted plants can be a problem. UGFs cause too much water circulation which make the plant grow either not grow at all or has slow growth. This happens because of aerobic changes produced by UG filter gear. What you need to do in this case is to use different types of plants that can be easily blind potted in trays or clay pots like Sagittarias, Crypts Swordplants and Vallisnerias.

Cannot Be Used UGF With Diggers: Channeling problems can arise with UG filters when organisms dig out the substrate with their extensive burrowing. Chaneling causes water to pass though these tunnels and circulation through the filter bed drops to dangerous anaerobic levels. You may need to use other filtration procedures along with UGF plates to take care of this problem and to stop channeling.

Trapped Fish: Fish seem to love hiding under UF filter plates. This is what causes trapped fish in the freshwater aquarium. Most fish will come out of under there after a while and they will be fine though. It usually happens that they come out for food when they’re hungry. But the UG filter doesn't have large openings like other filters through which fish may jump through. So while mishaps can happen, there is very less chance of it.

Difficult Long Term Maintenance: Using UGF is a lot like when you sweep dirt under the rug. The stuff that accumulates in the gravel and under the UG filter plates can be a problem. You will need to vacuum your substrate regularly and change the water. Of course filtration methods do have their small problems and this is the issue with UGF and can be handled by taking care not to overfeed or overcrowd or ignore regular maintenance. People have been known to use UGF safely for years.

Undergravel Filter Manufacturers

• Perfecto
• Top Fin