Complex sentence: Turtles require heat and sunlight (either natural or artificial) to properly digest food and develop their shells and beaks, so fluorescent UVA/UVB lamps alone are not suitable for turtles and should be supplemented with an additional radiant heat source.
Split into simpler sentences: Turtles require heat and sunlight (either natural or artificial) to properly digest food and develop their shells and beaks. Fluorescent UVA/UVB lamps are not suitable for turtles when used alone, and should be supplemented with an additional radiant heat source.