Aquarium Light Tips

Fish don’t need so much light as the plants do. A dim light is sufficient for fishes - usually just enough for them to see food. Very few fishes will eat in the dark. An exception is the Catfish; Catfishes, as a group, are largely nocturnal in their activities.

When no light reaches the fish tank, a great change comes over the fishes. Switch a light on suddenly after a protracted period of darkness and you will find most fishes in your tank are motionless. With few exceptions you will find that their color has faded. Such fishes have the brilliant red-and-green Neon fade to a white and light pink. Many fishes, you will notice, are lying on the bottom of the aquarium.

It should also be remembered that it takes some time for most fishes to adjust to a sudden light. If they are disturbed before their eyes have adjusted, they dash blindly about, even leaping out of the water. It is useless to feed them at this time, because they cannot see the food.

On the other hand, constant light seems to do no harm. Fishes in aquaria under constant light appear to live just as well as those that have alternate periods of darkness and light. The breeding cycle of many animals is controlled by the increasing and decreasing of the number of daylight hours as the seasons change. But very little work has been done with fishes in this field. What little has been done shows that light is a definite factor in the breeding of some, but not all, fishes.

Recently published experiments conducted with the young of certain marine fishes indicate that the fish will grow more vigorously when given a period of darkness in which to rest. How this affects the total longevity of the fish is not known.

There is no hard-and-fast rule governing light for the aquarium plants. It varies with the type of light, intensity of light, depth of water, kind of plant, the distance the light is from the water surface, and the amount of daylight that reaches the tank. Usually, if the fish tank is kept in a shaded area of a room, you should provide some artificial light in order to supply what the plants need. Lighting from a reflector which can be regulated is covered later.