Ornamental Fish Production and Management

4.2.1 Introduction

Filtration of aquarium water is an essential element of water management. The process serves two purposes:

 1. Maintenance of good water quality.

2. Partial correction (within certain limits) when the water goes wrong.

Good quality of water means a water that ensures a proper environment for fish to “drink”, “breathe”, “move” and even “pass metabolites” (excreta, urine and carbon-di-oxide) into it without becoming harmful to fish’s health and well-being. A water is said to be of good quality when its contents (chemicals, dissolved gases, organic matter) or condition (temperature and turbulence) are in a state which is good for fish, and is free from undesirable suspended particles and pollution. Pollution may arise from intrinsic (developing within the aquarium) or extrinsic (accidentally introduced) factors and will make the water wrong, weakly harmful or lethal to fish. Even a very well planned and properly stocked aquarium will need filtration in the long run.

In a filtration process the aquarium water is allowed to pass through a filter medium to cleanse it and is finally returned to it. Filtration is done basically in three ways:

(a) Mechanical filtration : Solid suspended particles are trapped and filtered out just mechanically.

(b) Chemical filtration : Harmful soluble chemical contents of water as those which alter its pH, impart it hardness or fish’s metabolites are rendered harmless by changing their chemical composition chemically.

(c) Biological filtration : Conversion of ammonia and nitrite which are highly toxic into non-toxic nitrates is done biologically by using a population of bacteria to feed upon the excretory products and similar detritus wastes.

Except the chemical filtration, mechanical and biological filtration combine in any filter eventually. All the three kinds of filtration process may be incorporated in a single filter. Accordingly, in a filter one or more filter media are used.

One has to be prudent in deciding which filtration to choose for a given aquarium. A number of factors need to be considered such as size, effective water volume and movement / turbulence and metabolic loading due to fish / other animals (stocking density and feeding and locomotory habit). On the other hand, it is also important to monitor filtration efficiency (filter volume and turnover rate) of the filter used in the aquarium which may be done by estimating the concentration of ammonia (NH₃), nitrites (NO₂) and nitrates (NO₃).

Filtration also helps in aeration by circulating the water of the tank irrespective of whether water is power driven or air-driven.