UMT MOOC: Ornamental Fish Culture - Topic 7: Seed Production - Factors to be Considered for Feeding - Light Intensity, Water Current, and Exchange Frequency

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Light Intensity
When breeding and rearing fishes in artificial or indoor environment, exposure to lighting have different effects on either fishes or plants. For plants or those doing aquascape, having more lighting means higher Photosynthesis output where light energy is converted to chemical energy as fuel. For fishes, higher lighting intensity and prolong exposure may not be beneficial. Any forms of light either sunlight or artificial light, depends on the intensity and exposure time, may increase the water temperature. Newly hatched larvae are very sensitive to light and water temperature. Such sensitivities can lead to head bunting, deformation in eye pigment, and mortality. Hence, to prevent this, we can use "Green Water" or water with algae to reduce such sensitivities. What is the recommended indoor light intensity? For 60 to 80 cm rearing tank, 20 watts with photoperiod of 12 hours light and 12 hours darkness.


Water Current and Exchange Frequency
Depending on fish species but the common approach is not to use water circulation during the larval stage. Apply gentle aeration (make sure the water is moving) only after 7 days and the bubble size through air stone or plastic tube should be as slow and small as possible. Aeration ensures good water quality and continuous supply of dissolved oxygen. Similarly, water change should not be performed on early larval stage until 7 to 14 day onwards. The volume of water exchange using aged or dechlorinated water should be around 20% to 30% by siphon technique every week.


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