Importance of Lighting	Turtles depend on full spectrum lighting, which is an artificial  illumination that will sustain their day/night cycle and help  them to process the nutrients of the food you provide.  A group of vitamins (specially D3) are absorbed into the turtle's body through direct exposure to this special light.  This absorption encourages proper bone formation and shell health.
Full spectrum lights	Your local pet shop should have a variety of full spectrum  lights specially designed for reptiles.  Most turtle keepers  recommend  Reptisun 5.0 or Vitalights.  Remember to add a basking area to your aquarium so that the turtle can get out of  the water and benefit better from your light.
Black lights	These lights emit a very dark purple beam and you have  probably seen them being used in plants.  Nevertheless, these lights are NOT Recommended for turtles since tests show that turtles benefit less from these types of lights and it will damage the turtle's vision due to the high intensity of the beam.  There have been cases reported of turtles that have been totally blinded by these lights in a short period of time.
Photoperiod	This is simply the duration of the period in which the light stays on and off.   If you wish to hibernate your turtles you will want to mimic the natural seasons.  Example:  provide more light in the summer since this is the season in which the sun lights for longer hours...