How does undergravel filtration work

This pulls water from under the plate, which in turn draws water down through the gravel. As the water passes across the grains of gravel, the nitrifying bacteria living there use the dissolved oxygen in the water to metabolize the ammonia and nitrite. The grains of gravel offer a huge total surface area for the bacteria to colonize, and the steady water movement ensures that enough oxygen will be available to support the large colonies.

As a result, the aquarium will house more than enough nitrifying bacteria to complete the nitrogen cycle, and the fish will have a healthy environment. In addition to being a biological filter, the undergravel filter acts as a mechanical filter because it catches solids as they pass into the gravel bed. Unfortunately, this actually works against the biological filtration process because as the spaces between the pieces of gravel fill with particles, the flow of oxygenated water past the bacteria is reduced.

Over time, the effectiveness of the biological filtration is significantly impaired. This problem can be solved by using a separate mechanical aquarium filter to remove many of the particles before they become buried in the gravel bed, and by cleaning the gravel when doing water changes.

An undergravel filter does not function as a chemical aquarium filter. Some undergravel filters are equipped with small cartridges of granular activated carbon that sit at the top of each lift tube, but these should be discarded for two reasons.

First, there isn't enough carbon in these cartridges to last more than a few days at the most. Second, these cartridges reduce the flow of water through the filter significantly. Sign up for our Newsletter! What are the ramifications of using undergravel filters vs power filters? Mode of Operation. Filtering Capabilities. Robust Mechanical and Chemical filtration.

Installed at the time of set-up and prior to adding substrate. Easy to install on the back or side of new and existing tanks. Comes in a variety of sizes and price points Fits on or in most styles of aquarium, including custom tanks Media mix is customizable Easy to access and relocate if needed Comes in budget and premium models Ideal for planted and fish-only community tanks 2.

Not ideal for debris removal or water purification Limits substrate options Only fit in some standard-sized tanks Harder to install and maintain Not ideal for tanks with moderate-to-high numbers of fishInstalled at the time of set-up and prior to adding substrate.

Slightly more expensive to buy and maintain Biological filtration is limited More complicated to operateEasy to install on the back or side of new and existing tanks. Not ideal for debris removal or water purification Limits substrate options Only fit in some standard-sized tanks Harder to install and maintain Not ideal for tanks with moderate-to-high numbers of fish.

Female Angelfish. Slightly more expensive to buy and maintain Biological filtration is limited More complicated to operate. Undergravel filters are inexpensive air-pump-driven devices that primarily offer biological filtration via the good bacteria in your substrate. Power filters have electric motors and are more robust and efficient. They offer customizable mixes of mechanical and chemical filtration media, and some have biological stages too.

Power filters are nearly always superior to undergravel systems in their filtering abilities. Undergravel systems work by using your substrate as their primary filter media. They typically include: plastic screens, plastic lift tubes and some pre-filled replaceable media cartridges. To assemble, attach the lift tubes to the screen and clip the cartridges to the end of the lift tubes.

Undergravel filters mainly provide biological filtration from the good bacteria in your substrate, which turn debris into plant food as part of the Nitrogen Cycle in your tank:.

These filters are cheap and available in a range of sizes that fit standard-sized tanks from 10 to gallons.

They work well for small planted tanks , since debris decaying in and under the substrate provides nutrients your plants can use. If a UGF is not maintained properly the media builds up an accumulation of detritus and other organic matter, which in turn contributes to a build-up of high nitrate levels.

Another factor is that underneath the filter plate, dead spots can form. This opens the door for the growth of unwanted bad types of bacteria that may contribute to poor water quality in the long run. The key to success when using a UGF is maintenance. With proper UGF care, these negative factors are greatly reduced and should not present a problem.

Here are some pointers to help ensure that your UGF runs properly:. As we have said before, get to know your tank and you'll be able to work out a regular maintenance routine that works best for your aquarium needs. Do your research on the various types of under gravel filters on the market, and how each works. Deciding to use a UGF or not is something you will have to figure out for yourself. Estuarine Aquarium Keeping for Beginners. Actively scan device characteristics for identification.

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