Water to fish is like air to humans. Fish will not survive if water is polluted with harmful toxins or the chemistry of water is not suitable for their survival. Different species of fish require a different range of water conditions for their well-being. However, most fishes are able to live happily within a common range of water conditions.
As hobbyists, we group them together and provide them with the best conditions for their survival within an aquarium.
Fishes selected for a community tank must be able to tolerate the same range of water conditions such as water hardness, temperature, and pH level; otherwise, some fishes in the same aquarium may look sick while others seem to be very healthy. Poor water conditions lead to stress in captive fish. Stress weakens their immune systems, leading to increased susceptibility to disease. Some of the most common stress problems and their causes in aquarium fish are:
- High ammonia (safety level = below 0.02mg. /litre), nitrites (should not exceed 10mg/litre.), and too high nitrates (should not exceed 50 mg/litre) content in water.
- Water fluctuating more than +/- 10o C per day for several days. The temperature may be increased or decreased by 10 C per minute slowly.
- pH fluctuations should not be greater than +/- 0.3 units per day. Keep pH levels as constant as possible and if necessary adjust gradually in steps of not more than +/- 0.3 unit per day.
- Wrong pH, temperature, water hardness or softness can cause stress and slow death.
- Overcrowded tanks, insufficient oxygen (poor aeration) can also leads to stress and death. Maintain at least 3 mg per litre of dissolved oxygen in water.
- Incompatible species in the same tank lead to cannibalism — a great stress situation for the poor smaller sized population.
- Toxins in water due to accumulated toxic chemicals such as heavy metals or insecticide sprays.
- Rough handling of fish — use proper sized net to move fish from one tank to another. Do not use your hands to catch them.
- Complete change of water in any aquarium daily can also cause stress. To avoid unnecessary stresses do not change more than 25% of water daily.