The only ones who have broken glass are over 7 inches long. These are 4 inches. A long way to go. Me and friend hve bunch of peacocks, not one broke a tank. ALL tanks were glass. depends on there personality. I'll say 75% of mine were docile. Even the aggressive ones didnt break glass. On note any smasher mantis can crack glass tanks, it is just that peacocks and chiragas are more likely, too. Peacocks are one of the most colorful though... Sleep on it, pray on it , get back to me through a PM or email.