Differences between mysis shrimp brands

[Aquattro]

Richer, I know the difference between Hikari and PE mysis is the source. PE is freshwater mysis, whereas Hikari is marine. Whether there is a difference between marine brands, who knows.
As for the fish, generally they need to spit stuff out for the first few times you try it. I use the PE mysis, and I've never seen anything NOT eat it. Maybe try some of that.