I don't know how much those cleaning crystals are, but I've been using Efferdent twice/day. Just drop in my aligner, leave it for 15-30 mins while I'm eating, and they're spankin' clean! I'm really pleased because I'd heard that these things can get icky, and when I finished my last one, it was as good as the new one.
Efferdent is really inexpensive, so I don't mind using it 2x/day.