Board Thread:Dragon City Gameplay Questions & Answers/@comment-24105783-20131119033003/@comment-24143352-20131119044953

My best suggestion would be to just do some trial and error with crystals once you get them. It's not really worth it trying to come up with some grid where you'd maximize your space. You won't have enough habitats to maximum crystal coverage anyway.

To the "bug", I've noticed it too. That is probably one of the reasons why the game crashes so much on iOS, it is conflicting with the facebook increments and the iOS.