Crested usually get all their need when it comes to calcium etc from their food so I would not worry about the water.
As far as LED they usually do not make much heat if they do it could actually become a problem, the most important is that your LED emits full spectrums rays because while not needed for your geckos they will be needed for your plants, this is what I use https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 which fit in the zoomed naturalistic hood (allowing a bulb for heat and one for light)
Again heat is fine but within reason for heat I actually use 60 watts black light which raise which raises the temps and allow for night time viewing without disturbing your animal, if you need heat you will likely need it day and night, and a LED light would interfere with your crested night and day cycle.
To know how a heat bulb raise heat based on wattage and enclosure height I encourage you to read this http://www.exo-terra.com/download/me...nterzoo_EN.pdf (starting page 33)