Toronto Pet Club

Should You Keep Aquarium Lights On At Night. This will give the fish a sense of day and night, even in an enclosed aquarium with artificial lighting. Whether 'tis nobler to give your fish a bit of darkness in the evenings, or risk stressing them out with a perpetually lit tank?

What is the light in a fish tank for? (Do you really need it?)
What is the light in a fish tank for? (Do you really need it?) from aquagoodness.com

When you switch off the lights at night, the plants will burn the stored starch enabling them to grow. As most fish require both periods of light and darkness each day, turning your aquarium light off at night is a good idea. How do i set up an aquarium light timer?