Agreed. Add another 100 gallons to that setup and you'll be good for an adult pair of fimbriatus. They really do require (and deserve) more space than 55 gallons. A 3' x 2' x 2' enclosure is 90 gallons or so, and would be considered a good size for a single adult. With a pair, you'll want to up the gallons.
This is a good place to gain knowledge, but I think you should have gained that knowledge prior to your purchase. That being said, the geckos are in your hands now, so at this point you should simply try everything possible to make those hands capable with the species. Read as much as you can on this site, and try to get an appropriate enclosure together as soon as possible. It would really be a shame to lose those gorgeous geckos, so I'm sure you'll do everything you can. Good luck and keep us updated if at all possible, I'm sure everyone would love to see those guys in a nice 100+ gallon enclosure!
Cheers,
-Matt