The numbers just mean what percentage of the bulb's output is actually UVB so a 5.0 bulb is putting out 5% of it's light as UVB while the 10.0 bulb puts out 10%. Since every bulb manufacturer is different, a Reptiglo 5.0 will not necessarily provide the same amount of UVB as a Reptisun 5.0. Also, the higher the percentage that is being generated as UVB, the lower the percentage of visible light there will be, so it may actually look like less light than a lower number bulb. Confused yet?
If the ESU fixture is made to hold regular household incandescent light bulbs then it should fit hold the compact flourescent bulbs too. If you only have 10 inches between your fixture and the basking platform then you might want to get the Reptiglo 5.0 instead. If you get the Reptisun you will need to raise the height and/or use the screen for the first few weeks until it "burns in". During the first 2 weeks a new CF bulb will produce much stronger UV than normal. You will also need to watch closely for any eye irritation on your turtles to make sure the light is at a safe distance. I haven't heard anyone have any problems with the Reptiglo bulbs however.
Thank you David you have helped a bunch so I will make sure to get the 5.0 Reptiglo.I am guessing the ESU Reptile Bi-Lights just clings on to the side of the tank .It says it has 2 sockets one for a daylight lamp and nocturnal lamp for the other.Do I have to use both sockets?
You're welcome! Actually that lamp fixture should be perfect since you want a UVB bulb and a heat bulb. So put your Reptiglo compact flourescent bulb in one socket and a regular household light bulb in the other socket for heat.