All of my fishes absolutely murder this stuff. I don't know what they put in it, but even my vegie loving mbuna's will kill for their share of this stuff. My only niggle with it is that it never floats, even though some people have indicated it does, and it is so hard you either have to presoak it for a hundered years, or as I do, crush it up for the fish to eat it.
As for the value, I got the 45 gram jar for only $1.99 and it lasts forever, as I only feed it 2 or 3 times a week as a supliment.