• Brief essentials

    Light is a critical factor in the ecology of every aquarium. That is as true of freshwater aquariums as it is of marine water aquariums but it is not so much the animals that need the light as the plants and (in marine water) the corals.

You should be familiar with these principles and rules

Why do I need light in my aquarium?
In a freshwater aquarium it is light which gives plants the energy for photosynthesis and growth. Plants will decontaminate the water, extract their basic nutrition from algae and provide the oxygen for fish and the other inhabitants in the aquarium, to breathe.
Obviously, no “plants” in the everyday sense, will grow in a marine water aquarium where light influences the growth and colouration of corals. Light feeds the plankton and symbiotic algae (zooxanthellae) which live in the tissue of corals and nourishes them.  

What about daylight?
Your aquarium should receive the minimum possible amount of natural daylight (which alone is not sufficient for the purpose) and combined with the artificial lighting in an aquarium, the amounts may change. Often the presence of indirect light will be responsible for considerable growth in algae.
In no circumstances should an aquarium ever be exposed to direct sunlight – if it is, the temperature of the water may increase to an excessive extent.

How much light will the animals need?
Most of an aquarium’s inhabitants only need a little light. For many of them it will be enough to find their way around, find their food and reproduce but the lighting needs of different animals and individual species of fish are quite different: some even need light to grow.

How much light is needed?
• As in the natural world, the rhythm of day and night must be maintained in the aquarium. That means that there should be about 8 – 10 hours of light a day – ideally always at the same time of day (timer).
Plants need a period of at least six hours of brightness if they are to make adequate
use of the light.

• If you would like to have you aquarium lit at night, simply switch the light on later in the morning or programme a break in the middle of the day (2 – 4 hours.) Interrupting the light in this way will also inhibit the growth of algae.

Caution:A break in the middle of the day should only be used in the case of a fresh water aquarium. In the case of a marine water aquarium it would be harmful.

• To avoid any sudden changes in the level of light, you should simulate a slow sunrise and sunset, gradually switching the lights on or off (where there are number of light sources).

• If you want to make a fundamental change to the periods of lighting, you should do it in stages (of about 30 minutes each) so the animals and plants can get used to the new timing and adjust their bio-rhythms gradually.