The varied forms and fascinating beauty of ornamental fishes have been attracting people from time immemorial. In our country many households keep aquarium fish in the living room. Keeping fish in aquarium tanks, though a fairly costly affair, can be profitable when compared to other hobbies.
With the development of modern aquarium technology it has become very easy to maintain and display some of the most beautiful living creatures in a controlled environment. However, the aquarium management calls for meticulousness and thoroughness as we create a specific isolated aqua-ecosystem.
First things first
An aquarium tank is first required to keep ornamental fish. It is a container which displays the aquatic organisms in a simulated natural environment maintained to some extent by introducing aquatic plants, rocks, gravel and other artificial décor. A closed ecosystem is maintained by regulating various biological as well as physico-chemical parameters with the aid equipment that control aeration, water movement, temperature, suspended organic matter, illumination, etc. besides feeding.
Aquarium tanks are commonly made of glass panels of suitable thickness (normally five millimetres), framed in iron or aluminium angles with the help of bitumen. Nowadays glass aquariums made without metal frames are more popular. Glass panels of such tanks are very strongly joined together with the help of silicon runners.
A cover is essential to prevent dust, household spray, house the electronic fittings and also to prevent the escape of fish. The inside of the cover should be painted white or coated with aluminium foil for reflection of light, for which a fluorescent tube is an ideal source as it highlights the attractive colouration of fish.
A fully furnished aquarium is heavy, so it should be kept on a strong stand or table of appropriate height. The tank should not be placed at a site where it faces direct or excess sunlight. It may cause over heating and algal growth in the tank. In order to get a good view of both the fish and plants in an aquarium tank the light should come obliquely. Hence, instead of in front of a window sill, a site nearer to its side may be selected. Further, regarding the choice of window an eastern exposure is preferable.
Now what would be the ideal number of fish in a tank? Number depends on the tank's carrying capacity, which is determined by the available total open water surface area through which oxygen is diffused. The greater open-water surface of a bigger aquarium will support a greater number of fish. Carrying capacity can also be increased by using aeration and effective filtration systems. As a rule of thumb, for fresh water aquarium fish require an area of 20 cm square per cm of body length (excluding tail). A tank of 60 x 30 x 30 cm will have a surface area of 1800 cm which is sufficient to hold 90 cm of fish.
Anyone who wants to keep ornamental fish should know the steps of setting up the tank. If the tanks are purchased, they should be checked for leakage, their sides should be cleaned with one per cent potassium permanganate solution, besides repeated washings with tap water.
The next phase of the setting up of an aquarium is the selection of small stones and fine gravel for spreading at the bottom of the tank. For aquariums without biological fitters, arrangement of smaller stones should be made in groups at the bottom, after which the gaps should be filled with fine gravel. Then the gravel bed is covered with a layer of coarse river sand.
Ground layer should be 3-5 cm thick and should slope slightly towards the front of aquarium. Over the coarse sand, some fine sand is spread. For aquarium tanks where biological filters are to be set up, 3-6mm sized dark particles of granite, basalt, quartz or slate would be ideal as bottom materials to help filtration.
Calcareous rocks and coral stones should not be used as they may affect water quality by altering the pH value. The particles should be washed in tap water several times before they are used. Keep an eye out for my next article where I would like to provide details regarding filter, water quality, planting, lighting, etc.

Dr Sagir has recently completed his doctoral thesis on ''Utilization and effectiveness of ICT for disseminating agricultural technologies among the farmers'' from Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur. Write to Dr Sagir will all your questions related to pets at [email protected].