Under Gravel filters (UGFs) are a type of filter which water is drawn through a plastic grate that lies under the gravel bed. Normally these tanks are limited to gravel substrates as sand will fall through the grate and will not allow the (UGFs) to function properly. This type of filtration uses mechanical and biological filtration. The gravel acts as a mechanical filtration as it collects the debris. The biological filtration comes into play when a bed of bacteria grows with the help of the oxygen-rich water that flows through the grates.

UFGs are great for any aquariums that require good filtration. The gentle flow with an air stone will make them great for fry, shrimp or even a betta tank. However, it must be noted that these types of filtration require a pebble or stone substrate to function properly. Also, these filters are relatively cheap and will last you a very long time.

Many people might criticize the use of an Undergravel Filter. Normally they assume that these filters are “Outdated” due to the other different types of filtration that have come onto the market. Another criticism is that when the gravel filters are in use, more detritus gets stuck in the gravel bed. Over time, this clogs the filter and limits the (UGFs) to work properly. Also, when using under gravel filters you are limited to certain substrates that allow (UGFs). Planted tanks are questionable as well. Since deep rooting plants will have a hard time when a (UGF) is in place.

With an under gravel filter you will need to clean the gravel regularly. The easiest way to do this is by using a gravel vacuum you can find at your local pet store or online. This is necessary to prevent the gravel from accumulating too much debris. Which would cause your filter plate to be clogged and not allow enough oxygen water to reach the good colony bacteria bed. This will result in lower water quality.

There is no doubt that under gravel filters aren’t for every tank. They do not provide any chemical filtration and can be noisy when using an air pump. However, when properly maintained, under gravel filters are easy, inexpensive and low maintenance for most beginner tanks.