That's the same food I feed my embers, they don't seem to have a problem with it. You can try grinding it a bit with a spoon and see if that helps though. Either that or they don't like the taste; mine seem to like it but maybe yours are finicky.
You can also try soaking some in Garlic Guard, see if that helps make it more palatable for them. Hikari also makes a small fish pellet you can try.