User blog comment:FairyRaven/Fairy Tail Chapter 394: Juvia vs. Keith, Review and Commentary/@comment-2214433-20140725134525/@comment-24066070-20140726011305

Maybe it will be like Natsu's Lightning.

He'll be able to use it, but it will exhaust him much faster than normal Ice-Make and perhaps Gray won't be able to eat any ice created through Ice-Make, since it is too similar to his own magic (meaning he can't eat Lyon's ice since they essentially use the same magic)