1. WATER QUALITY MANAGEMENT IN ORNAMENTAL FISH CULTURE

2. Introduction
Water is the prerequisite for the maintenance, breeding and culture of tropical ornamental fishes.
For ornamental fish farming water is mainly obtained from rain, river, artesian well, canal and reservoir.
The physico-chemical characteristics of water such as pH, hardness, temperature, dissolved oxygen; chlorine and carbondioxide content play a key role in the breeding and production of many ornamental fish species.

7. pH
The pH of water usable for ornamental fish farming may vary from acidic to alkaline depending upon its source and chemical and biological factors.
The optimal pH for the growth and breeding of majority of the ornamental fishes may be neutral or slightly alkaline i.e. 7-8.
Some ornamental fishes such as oscar and discus will spawn only in slightly acid and soft water.

8. pH … contd
Water in ornamental fish tanks should never fall below 5 or rise above 8.5.
Ornamental fishes preferring slightly acidic pH (6.2-7) include rosy barb, tiger barb, tetra, angel and danio.
On the other hand, certain fishes like cichlids, goldfish, koi and gourami prefer alkaline pH.

13. Chlorine
Ornamental fish culturists in cities often have water quality problem as the tap water used by them contains chlorine beyond permissible level.
The growth and survival of any sensitive fish are affected by chlorinated tap waters.
Chlorine content as low as 0.1 ppm itself is toxic to fishes.

14. Chlorine The high chlorine content of such waters can be dechlorinated
by heating the water.
Water with chlorine will have to be kept over night for the escape of chlorine

15. Water hardness
It is nothing but the total soluble calcium and magnesium salts present in the water expressed as its calcium carbonate equivalent.
The total hardness of water however, includes the sulphates and chlorides of calcium and magnesium.

16. Water hardness
The total hardness is mainly used to classify waters into
Hard water or
Soft water
Total hardness of 50 ppm calcium carbonate equivalent is considered to be the dividing line between hard and soft waters.

17. Water hardness …Contd
Water with hardness of ppm have been found to be optimal for the normal growth of majority of ornamental fish.
Water with less than 12 ppm require liming for higher production of fish.
Water of less than 5-ppm hardness have been found to affect growth and eventual death of fish.

18. Water hardness …Contd Hard water is also known to influence
feed intake and
growth of most cichlids
angel,
black zebra,
firemouth,
blue morph and
auratus.

19. Water hardness … Contd
Soft water fishes viz. tiger barb and rosy barb do not show maturation above 120 ppm hardness.
While koi, angel and guppy prefer soft water for better growth, and colouration,
Mollies and platies prefer saline and hard waters.

20. Water hardness … Contd
Successful spawning of goldfish has been reported at 700-ppm water hardness.
Oviparous goldfish and koi carp prefer carbonate hardness for maintaining sticky nature of eggs and associated incubation conditions.

21. Carbon dioxide
Like other food fishes, ornamental fishes are also known to avoid dissolved carbon dioxide content above 5 mg/l.
However the ornamental fishes can tolerate high carbon dioxide content of the water
The presence of high carbon dioxide level in water may hinder the solubility of oxygen.

22. Carbon dioxide
The carbon dioxide concentration increases in ornamental fish ponds and tank during night and decreases during day time.
Free carbon dioxide at a concentration of more than 15 ppm is detrimental to ornamental fishes.

23. Temperature
Water temperature is one of the most important factors influencing the breeding, rearing and transport of tropical fishes.
Majority of the ornamental fishes tolerate water temperatures between 21 and 30oC,
28oC, have been found to be most suitable for the breeding of tropical ornamental fishes.
In order to maintain optimal temperatures, suitable devices have to be used.

24. Temperature … Contd
Koi is known to tolerate wide variations in temperature i.e. between 20 and 30oc.
Dwarf cichlids require optimal temperatures of 26-27oc.
Swordtails are very sensitive to 25 – 27oC.
Good growth and production of dwarf gourami Colisa lalia have been recorded at 26 – 28oC.

25. Temperature … Contd
Spawning of goldfish has been successful in 24 – 26oC.
It has also been found that 22oC is more suitable for rearing eggs and larvae of goldfish.
Guppies and mollies will be seen active at water temperature of 25 – 27oC.

33. Nitrite
The nitrite is produced in the waters through nitrification process of toxic ammonia.
The nitrite concentrations above 1 mg/l may impair the health of the fish.
The toxicity of nitrite increases with decreasing pH.

34. Nitrate
Ornamental fish can tolerate nitrate levels between 50 and 100 ppm.
The aquatic plants however, utilize accumulated nitrate in the water of the ornamental fish tank.

35. Oxygen
Dissolved oxygen content of the water plays a crucial role in fish culture.
Fishes of aquarium tank would be under stress and be liable for parasitic attack if optimal oxygen levels are not maintained.

36. Oxygen
The solubility of oxygen in water depends on its temperature and also on the rate at which it s kept in contact with water.
Oxygen dissolved in water by direct diffusion at the air-water interface.
Further, it is also made available by the presence of aquatic plants.

37. Oxygen … Contd The oxygen level of aquarium tanks can be enhanced by
Constant aeration,
Circulation of water,
Sprinkling of water.
Surface agitation, etc.
The surface agitation apart from enhancing the oxygen level, drives free carbondioxide from solution

38. Oxygen … Contd
The temperature and solubility of oxygen are inversely related.
As the temperature increases, the oxygen holding capacity of water decreases.

39. Oxygen … Contd
Generally many species of ornamental fishes cannot tolerate waters containing less than 3 ppm dissolved oxygen.
For example, gold fish shows impaired activity at less than 3 ppm oxygen level.
An oxygen level of above 5 ppm is advisable, not only to supply the oxygen needs of the fish, but also to limit ammonia accumulation.

40. Biological filtration
Excreta of fish and unused food materials often lower the oxygen content of water in tank.
When such condition arises, the water has to be changed at least once in two days.
Otherwise, optimal survival of fish cannot be expected.

41. Biological filtration
Home aquarists are therefore forced to make alternative arrangements for changing water in such tanks.
In this connection, biological filters could be used in ornamental fish tanks to help in aeration and maintaining the quality of water.

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