Learn About Undergravel Aquarum 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 reasonable-sized aquarium.

How Do Aquarium Undergravel Filters Work?

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 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 paraticulates 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).

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

Disadvantages of Aquarium Undergravel Filters

The main drawback to undergravel filters is that they are not adequate as the only filter for a large tank (more than 15-20 gallons of sparcely populated tank). They 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.

Because they do not hold enough surface area for a large amount of beneficial bacteria, they do not cleanse the tank of enough toxic ammonia and nitrite for fish health. More fish die from ammonia build-up than from any other water problem.

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.

An undergravel filter is the first and primary step toward tank filteration, and nearly every tank that has more than about 1/2" of gravel must has one. However, we also suggest that you add a Power Filter or more. Learn more about Aquarium Filtration in General HERE