People who keep fishes in Aquarium has always this question in mind “Does my fish need light”?
Lights in given in aquarium for many reasons and not just for fish. Light helps people to see the fish and enjoy, its the other way, not that fish need light to see a human.
The second reasons light is necessary in aquarium when you have aquatic plants and plants do need light for photosynthesis.
Some of the fishes can see without visible light, which means that they are able to see using ultraviolet lights. But it really depends on the depth of the water where they are found.
Water absorbs visible light so in ocean only ultraviolet light is able to reach such places where visible light is not able. Fishes found in those depths use UV rays to see things but fishes found at the top they can see things clearly using visible lights.
Yes, fishes in Aquarium do need light to see but not always just like day and night. In Aquarium, more than fishes plants need light.
You need to make your aquarium like a natural pond because fishes that live in pond can’t see using UV rays. In pond, during day time it’s brightness and during night time it’s darkness same thing applies to aquarium.
It is better to switch of the lights of aquarium and let your fishes sleep.