yes they do jump if the water level is too high or they dislike the bowl. i haven't had that happen in a while. back when i had SS crystals in here, i mysteriously lost a lot of them over the course of a 2 week vacation i took. it was summer, it got past 80F in the bowl, they probably hated it and either died and got eaten by the survivors, or jumped out. i never found bodies anywhere though...maybe they jumped far.