Wow that sounds like a SCary Pet Shrimp to Keep! =^___^=
think the minimemum size is 25-30gal. Should be okay i think =D
CAn reach 7" Long! Fun Fun! And Eats Yummy Yummy Live Food and other crab, snails, crayfish and Friends =D Just no mixing with other live stuff and most corals, Mr Mantis Shrimp is a very picky interior designer! even if if u try to show him ur designs he'll say no no no and always insist on his way. Best not to mess with his designs or else hell smash ur hand apart! Eeekk =S
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Also make sure ur tank glass is very thick and strong, other wise mr shrimp can turn into.. Dont touch me! Hammer Time! *Dances then breaks glass*
I think these guys are pretty hardy to keep! No Kidding! =^___^=