Whats worked for me in those cases is mixing live brine and frozen mysis and feeding several times a day this way. If they start eatting the frozen mysis here and there you can use less live brine each time and get them to completely accept frozen mysis. Depending on the fishs size PE mysis is larger and hikari mysis is smaller. I would probably start with hikari mixed with live brine 3 times a day. Getting 250 live mysis is nothing, and IMO would be money wasted.