VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

SETTING UP OF AN BIOLOGICAL FILTER AND AERATION

• Rain water free from contaminants or tap water is ideal for aquarium tanks. As tap water of domestic supply is likely to have good amount of chlorine which is harmful to fish, the same may be stagnated for about one or two days followed by subjecting it to strong aeration before use. If the water is hard, it must be suitably treated. The temporary hardness which may be due to the carbonate of calcium and magnesium should be removed by boiling the water. On the other hand, the permanent hardness due to the dissolved sulphates and chlorides of calcium and magnesium is removed by treating with washing-soda (sodium carbonate). The latter reacts with sulphate and chlorides of calcium and magnesium, and dissolved state of sodium sulphate. For reducing the hardness of water, it is advisable to mix up water with soft water such as rain water.

Biological filter (Biofilter) and aeration

• Biofilters helps in the
  • Removal of ammonia from the system with the aid of microorganisms colonizing tfhe biofilter media
  • Removal of nitrites
  • Remove dissolved organic solids
  • Addition of oxygen
  • Removal of carbon dioxide
  • Removal of excess nitrogen and other dissolved gasses including abnoxious gases
  • Removal of suspended solids
• A biofilter comprises of corrugated and pored asbestos or acrylic plate fixed about 10 cm above the bottom with a non soluble adhesive on all the sides of the tank. At one end of the plate a glass cylinder or a plastic pipe of about 8 cm diameter opened at both ends is inserted through an opening made in the plate. After fixing the plate, the gravel is spread over the floor of the plate to a depth of 5-7 cm. The gravel terrace should slope from back to front, in order to give a better appearance. Subsequently, well washed and fairly round edged granite and other suitable aquarium stones may be buried underneath the gravel terrace. As far as possible, coarse gravel should be avoided, as food particles may get caught beyond the reach of the fish in the interspaces of gravel affecting the quality of water. Further, through coarse gravel water flow may be too fast and the biological filter will not be efficient owing to the limited surface area and poor development of bacteria.

• In order to maintain the equilibrium of carbon dioxide and oxygen in aquarium, partial water changes every two weeks may be adopted. Alternatively, the aquarium water may be aerated particularly during night, when the carbon dioxide level goes up due to the respiration of plants and fish. Aeration may be done by providing a small piston or diaphragm-type aerator, polythene tubing and an air-diffuser stone. The latter is lodged in the cylindrical glass set or a plastic pipe up of the aquarium tank. When the air reaches the air stone, owing to the porous nature of the stone, air bubbles are released which will oxygenate the water.
• The water of the aquarium tank is likely to get polluted due to the excretory products of fish, plants, dead organisms and uneaten food rich in nitrogen compounds. Unionized toxic gaseous ammonia is formed directly through the excretion of gills and indirectly from various excretory products such as urea, uric acids and amino-acids which are mineralized by the action of bacteria to form ammonia. An ammonia concentration beyond 0.5 mg/litre is toxic to fish. When the fish are exposed to high levels of ammonia, the haemoglobin of the blood losses the ability to combine with oxygen or to liberate carbon dioxide.
• In aquarium tank, where biological filter is fixed, the water used by fish and loaded with ammonia passes through the gravel bed and filter plate and gets stored at the bottom-most chamber of the tank. i.e., below the biological filter. While passing through the gravel bed, the water loaded with ammonia passes through the filter medium during which  the aerobic nitrifying bacteria such as Nitrosomonas and Nitrobacter acts on the ammonia in the water. Nitrosomonas oxidizes ammonia to nitrite, which is further oxidized by Nitrobacter to nitrate.  Thus, the nitrate loaded water which occupies the lowest chamber of the tank lifted to the surface and circulated again and again.

Nitrogen cycle-animation

• The water must be filled in the aquarium tank without disturbing the bottom stand. This may be done by means of a hose pipe running first into a cup kept on the aquarium bottom. The overflowing water from this cup will gently fill the aquarium tank without disturbing the bottom. In this way the aquarium tank can be first filled to about 5 cm and then filled directly.

Aeration pump