I don't think the ReptiGLO 5.0 is strong enough use with a bearded dragon. The only reptiglo I've heard being recommended as decent is a reptiglo 8.0, and anything lower than that puts out less UVB. The most commonly recommended flourescent tube bulbs are:
ReptiSUN 10.0
ReptiSUN 5.0
ReptiGLO 8.0
Unfortunately the numbers aren't consistent across brands - for instance, the reptisun 5.0 is actually slightly stronger than the reptiglo 8.0 which can make getting this lighting stuff right a bit more confusing.