Many people keep peacocks in glass tanks sucessfully. The only person on RC I know of that has witnessed a tank smash is Dr. Roy, and he studies them for a living so yeah...Put down the acrylic bottom, put a few inches of sand on top, and don't tease the mantis and you should be fine. Also you can keep corals with peacocks, but make sure to keep the light PC and under as light is a major contributor to shell disease (you didn't ask, just sayin in case you hadn't come across that bit of info
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Dan