Why is lighting so important for aquariums Firstly, sufficient light allows people to have a better view of the fish and plants in the aquarium tank. With sufficient light, the fish and plants look much clear and more beautiful. Secondly but the most important, proper light can provide integral energy to the fish and plants. Light is essential factor for any living system that need photosynthesis, such as algae, anemones and coral and other underwater living plants. Thirdly, proper light also influence the behavior and physiology of fish. In a word, proper light is integral for the overall health of the entire aquarium ecosystem.