Mandarin questions

[trilinearmipmap]

So as far as the two sizes of PE mysis, my fish don't like it much because it seems pretty big (about 1/4"" size), I bought a large slab of it from Ocean Aquatics, so I guess I need to buy the smaller size of PE mysis, is this commonly available? My mysis was not labelled at all, just a big huge freezer pack that I was told was PE mysis.