It's perfectly normal for fish to get finicky, not wanting to eat anything they aren't used to. If the fish food is better quality (which it is better than Tetra flakes), it's still worth transitioning the fish over to eating the new food. Just takes some time until they accept it. Just starve them for a couple days or so before feeding it (when they are hungry enough they will eat the new food). Or you can slowly introduce it to them, by adding/mixing it in with their current food during feeding. Or you could add more enticers/attractants to the food, such as Garlic oil (or Seachem Garlic Guard) and the fish would be more willing to eat it up.
There is New Life Spectrum Finicky fish formula, purposely made for picky fish. It also a really high quality food, actually the highest quality I know of. It has New Zealand Green Lipped/Shelled Mussels and Garlic, both of which are a favorite taste/smell (attractant/entice) to fish, and not only that, they have great health enhancing properties. It is a pellet though. And just to mention, pellets and other denser foods leach out less nutrients (so they retain more nutrients for your fish to consume) into the water than flat flakes that have more surface area. Thera A is also a good NLS formula, with more garlic, but no mussels.
But you already have the Omega One flakes and they are a pretty good food so it would be good to make use of it. Just takes some time to transition some fish over to a new food. I do incorporate the same Omega One formula into my own fish's diet every so often to change things up (I use the pellet form though).
psychedelic made a good point, if the flakes are large, the fish will suck them into their mouth and munch on them and sometimes end up spiting some of it back out, but they still may actually be eating some. But I am sure Patriot knows that they are in fact just sucking it in and spitting it out without eating any of it, which is just the fish being picky.
