IME it's a rare occassion when a freshwater species of fish (short of some of the more extreme picky eaters - some puffers, Asian aros, etc - at least not in quantities to feed it exclusively) can't be trained to eat this food. That includes many wild caught specimens that had never seen a pellet in their life, as well as numerous species that had been started on other commercial products, including flake food. Some of these fish had spent their entire life eating nothing but live food.
Sometimes it takes some serious tough love, and/or one has to be creative in their training methods. If V. lionfish can be trained to come to the surface and eat pellets, then certainly most freshwater species should not be impossible to train to do the same.
On a side note, the creator of NLS was the first person in North America to import P. polleni, and successfully breed them in captivity. One of his polleni can be seen on the cover of the June 1993 edition of FAMA, as well as being featured in an article on the 1993 Florida Tropical Fish Farms Association annual show.