I mean through natural healing. Normally, you heal 1 hp nonlethal/HD/hour. It's probably not as much as it's taking, but it's not entirely insignificant, either.
Since this is
starvation damage it won't recover from natural healing, since "Nonlethal damage from thirst or starvation cannot be recovered until the character gets food or water, as needed—not even magic that restores hit points heals this damage."
Hmm, for some reason I thought rest was needed to rest to recover nonlethal damage, which a creature shouldn't be able to do while it's taking ongoing damage, but checking the SRD it just says "You heal nonlethal damage at the rate of 1 hit point per hour per character level."
It'd be easier to just clarify it, like this:
Crystal Storm (Su): Once per day, a demarax can unleash a 20 foot burst of whirling crystals. Any creature within the burst must make a DC X Reflex save or be struck by a crystal shard. A struck creature is afflicted by one of the effects at random from the table below for 2d4 rounds:
1 - dazzled (–1 penalty on attack rolls, Search checks, and Spot checks)
2 - fascinated (takes no actions other than to pay attention to the fascinating effect)
3 - color spray (as the
color spray spell)
4 - sickened
5 - confused (may act, may not, may flee, may attack nearby creatures)
6 - baleful displacement (50% miss chance when attacking opponents)
A demarax uses this attack only as a last resort, since it uses up the creature's supply of nutrition. The demarax takes 2d10 nonlethal damage per hour until it feeds on a crystal. If a demarax falls unconscious from this nonlethal damage, it must make a Constitution check every minute (DC 10 + 1 per minute) or drop to -1 hit points and start dying, it then loses 1 hit point per minute until it dies or is fed a crystal (which immediately stabilizes it).
Since this nonlethal damage is caused by starvation, it can not be restored until the demarax gets food (see the Starvation and Thirst rules).