Learn About Aquarium Undergravel Filters


Undergravel filters are usually the first and primary filter used by the beginner aquarium hobbyist.

They are a simple solution to the complicated filtering needed by any small aquarium.

The filter "plate" is placed under the gravel. Tubes from the plate contain an air stone attached to the air pump (outside the tank). The air pumped through the air stone at the bottom of the tube creates an upward current of water that draws water from underneath the filter plate up the tube and back into the tank.

As the water is drawn from the tank, down through the gravel to the underneath area of the plate, it is filtered. Large particulates such as uneaten food and fish feces are left on top of the gravel (they are too large to get through the tiny gravel pores). Routine gravel vacuuming will pick them up and remove them from the tank. But a lapse of vacuum maintenance can allow them to decay and toxify the water.

Additionally, bacteria live in the gravel - bacteria that thrive on the biological waste from the fish metabolism and waste and the oxygen that is in the water. The bacteria "eat" the ammonia and nitrite, turning it to a less toxic type of ammonia and nitrate (a good plant fertilizer).

The main drawbacks to under gravel filters are that they are not adequate as the only filter for a large tank (more than 15-20 gallons of sparsely populated tank). And they require more maintenance than other types of filters.

More fish die from ammonia build-up than from any other water problem, and under gravel filters are abysmal at correcting that problem. The gravel simply does not have enough surface area for a large amount of beneficial bacteria to grow. Therefore, under gravel filters do not cleanse the tank of enough toxic ammonia and nitrite for fish health.

A heavily populated tank needs much more biological filtration than a sparsely populated tank because it produces more waste. Also, as your tank matures, the load grows. A saltwater aquarium needs considerably more efficient biological filtration than a freshwater tank needs because its inhabitants are infinitely more sensitive to environmental toxins.

See Recommended Undergravel Filters Here: Lees Brand:

Premium Undergravel Filter

Original Undergravel Filter

Under gravel filters also require more laborious maintenance than most other types of filters. Because the large particulates are trapped on TOP of the gravel, frequent gravel vacuuming is necessary.

An undergravel filter is the first and primary step toward tank filtration, and nearly every tank that has more than about 1/2' of gravel must has one.

Learn more about Aquarium Filtration HERE