05-19-2011, 11:02 AM
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Light and dark in the tropics is constant, and that is the more important issue here. As long as the fish have a reasonable period of total darkness--by which I mean, complete dark, no daylight, no room lights, no moonlight, nothing--of several hours they will be fine. If you never turned on the tank lights, and the room just had ambient daylight, your fish would be in "heaven." They don't need much if any light, and in most of their native waters it is very dim. |The day/night contrast is the critical thing.
My fish room gets daylight during the morning, through closed blinds, but the fish are awake and to them it is day. The tank lights come on at noon, and remain on for 9 hours until 9 pm; this schedule is solely for the benefit of the plants to prevent algae inctreasing. There is a room light that comes on just before 9 pm and remains on for an hour, to provide a "dusk" type period. Then the fish have total darkness until dawn, which varies from 7-10 hours summer/winter.