Which is better UVB?

[financier]

I am setting up my enclosure for my new baby. It is a 36L 18W 12H and was wondering what is better for UVB? Should I use the Powersun type which gives both heat and UVB or use a spot for heat and then a UVB tube that would give the UVB all through the enclosure. Thanks

[Fatal_S]

Tubes and florescents provide UVB for about 6 months, after that they're just lights. MVBs (Mercury Vapour Bulbs) provide UVB for the life of the bulb. So MVBs are a better buy in the long run. But... MVBs produce a lot of heat. They need a lot of airflow around them (cannot be enclosed in the tank or in a solid-dome-lamp). They also cannot be dimmed. So it depends on your tank.

Also, is the light going to be outside of the tank? If there's glass, screen or plastic between the light and skink, the UVB is rendered useless.

[financier]

Hi,,thanks for the reply.
The bulb will be outside the tank. I have a very open wide screen top. Not a fine screen like for doors. If a dome hood is not right, then what should I use to hold the bulb?
I am also worried alittle that it might make the enclosure to hot. It is a good size enclosure. PVC with a drop down plexiglass front.