. . .

Tropical Fish

Goldfish

 

Mechanical Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The main purpose for installing a filter into your pond is not to keep the water clear. Mechanical filtration removes solid organic wastes, such as fish droppings, Leaves, and other Organic waste, by trapping them in special filter media (Sponges, brushes or even gravel).

Mechanical filtration just removes solid wastes; it will not make your pond any healthier for the fish. The pre-filter attached to most pond pumps is a type of mechanical filter, put there to protect the workings of the pump from things such as gravel, and even fish. To keep the water healthy a biological filter must be used in conjunction with the pump and its pre-filter.

Biological Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . A biological filter acts as a home for billions of friendly bacteria that use toxic substances produced by waste in your pond as food. One type of bacteria convert highly toxic ammonia into slightly less toxic nitrite, and another type will convert the nitrite into relative harmless nitrate. See more on the Nitrogen Cycle.

The bacteria need lots of oxygen, so a continuous flow of water over the biological media is essential for their well-being, and for that of the fish. The minimum amount of oxygen that bacteria need to grow successfully on a biological filter medium is 5ppm. The most common type of biological filter used on ponds consists of a large box or compartment, usually containing a few layers of sponge matting and some biological media. Water is simply pumped out of the pond into the box or compartment, which usually sits above the ground. The water flows through the sponges, acting as a mechanical filter, removing small particles of organic waste, and then over the biological media, where the bacteria grow.

A good biological filter should have a long contact time, i.e. the time the water is in actual contact with the filter medium should be as long as possible. More contact time means more efficient biological filtration.

Cleaning Filter Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The sponges or brushes should be removed and cleaned regularly by rinsing them in pond water, not tap water. Tap water contains Chlorine or Chloramines and will kill the bacteria. It doesn't matter if they are 100% clean; the sponges usually work more effectively when they have some dirt in them.

The biological media, however dirty, should never be washed.

Ultraviolet Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . In order to keep the water crystal clear you might need to add an ultraviolet clarifier (UV). These devices sit above or near the box filter. As the water passes by it kills the free-living algae cells that makes your pond water green (Green Water). The UV tubes need to be replaced at least every 12 months, in order for them to work effectively.