If they arent happy, they will try to jump to the tide pool next door. Little do they know that that tide pool is dry. They need a deep substrate of varying sizes and lotsa rubble. Fwiw, I dont cover my tanks and my pearly is still there. IME the blue spot settles in faster/better than a pearly. Once they settle in, the risk of jumping is much less than it is the first day or 2.