I have six turtles in a 90 gallon tank. They are all over a year old, and get along well. My question is how much UVB should they be getting and how close does it need to be. I have read that the UVB lights lose there effectivness at a distance. The top of my tank is about 6 inches off the water. Is that close enough? Should I put it over the basking area instead of the water?
They are doing fine right now but I am conserned about their long term health.

