Are you referring to a Redfoot Tort? I would say you have a few options...natural sun of course....or a variety of mercury Vapor Bulbs according to the enclosure size...but with this species if you let them have good outdoor time for natural sun then you can get away without the intense type mvb that some use for the more "arid" (and I use this word as a reference and not in any way imply dry and NO hydration ) species...and if you are not in part of the world where the beautiful ball of fire is shining through..then you can also use a long tube uva/uvb bulb in conjunction with any type of heat bulb/source...
also,..the bulb you are likely referring to is a coil/pig tail type compact bulb..or the short U shaped compacts....which have had alot of issues in the past and I personally don't trust for a smaller indoor enclosure...
have been known to cause a painful condition in baby tortoises' eyes, similar to snow blindness. As soon as you stop using the bulb the eyes start to recover.
For a redfooted tortoise, your best bet would be to use a tube-type fluorescent bulb, with lots of plants to diffuse the light and provide shade for the tortoise.