The Importance of Light in the Tank

• It's important to have a light in your tank. There are many different lighting sources, each with its own benefits and drawbacks. What doesn't matter much is the kind of light. Fish are just like people; they do much better when they have regular intervals of lightness and darkness. If you also have live rocks or plants in the tank, they will need the light for photosynthesis, which is basically their sustenance. Every living thing in your salt tank needs light to stay alive.
  
  

The Importance of Darkness in the Tank

• While light in the tank is important, so too is darkness. Fish in your saltwater tank need the lights to be turned off, because in their natural habitat, the ocean, there is lightness and there is darkness. It is during the dark hours that the fish are able to rest, often in rocks or coral. The darkness triggers that it is time for rest, and many fish will take their cues from periods of lightness and darkness. Thus, it's important to try to mimic light and dark periods as they would occur in their natural habitat.
  
  

How Long Lights Should Stay On

• The advisable length of time for the lights to stay on in a salt water fish tank is anywhere from 10 to 12 hours. Some tanks can handle as little as eight hours of light, and some will do fine with 14 hours. Most tanks, however, do the very best with 10 to 12 hours of light and the rest of the time in relative darkness. Also, tanks that have lights on for more than 12 hours have a higher rate of algae. To keep your tank light and dark for appropriate periods of time, consider plugging the lighting system into a timer so even when you are not home, the lights are on or off when they should be.