What is a pump, a filter, an aerator for a tropical Fish Tank?

A pump is a mechanical apparatus which forces water or air through tubing or other equipment. It provides the flow that makes the filter and aerator operate.

Filters (except under gravel filters) are units containing (or being made of) a porous filter material such as activated charcoal or filter floss. There are a number of different filter types available, but the principle is basically the same in all except under gravel filters. Water from the aquarium is passed through the filter material and thereby cleaned.

An aerator is a unit that exposes water to, or mixes it with, air. As far as home aquaria are concerned, an aerator diffuser is usually a porous stone which is placed in the aquarium with connections so that a pump forces air through it. It serves the purpose of breaking the stream of air into small bubbles, thus increasing its effectiveness.

A water pump draws water from an aquarium through one tube and discharges it through another, the water circulating through the pump. Water pumps are usually employed only in larger indoor installations or in outdoor pools. They may be used to empty aquaria or to transfer water from one aquarium to another. They are also used when it is desirable to have the filter located some distance away from the water to be filtered. Another use, seldom encountered indoors, is to spray water for a fountain, or to raise water for a waterfall.

The filter material is the same as that in any other filter, charcoal, and/or sand, and/or glass wool. The filter is designed to be closed tightly when in use, provision being made to remove the filter material for replacement o cleaning. Circulation takes place through two nozzles. The water is sucked through a tube from the tank directly into the filter material. A perforated compartment receives the water after it has filtered through the matrix. A nozzle leading from this compartment directs the water through the pump and back into the aquarium.

This type of water pump usually provides faster and more efficient filtration than do the more conventional types of air-operated filtering systems. However, it does not agitate the water so efficiently as a good air stone; it is also quite cumbersome and usually more expensive to purchase than the ordinary setup.