Regarding the Cyanide method.
I am a newbie so flame if you must. But from what I have read Cyanide is a TEMPORARY thing. If the Powder blue survives transport, and then stays alive for about 2 weeks in the lfs, (that is if no one buys him first or if you can pay the $ and have the dealer hold it for two weeks) then you are past the critical time period. Additionally some dealers at least warranty the specimen for 2 more weeks.
(Wondering if there could be permanent organ damage as a result of cyanide exposure that might not be apparant for several months, so could be mistaken?)
Of course, other than the longevity concern, you may wish to refrain from purchasing this specimen on moral grounds due to destructive fishing methods.