I'm not sure how it's supposed to be pronounced, I've only seen it in print, not heard it. I say daf-knee-uh (emphasis on the first syllable) but I don't know if that's right XD
Yeah, I would recommend calling around if you don't have anywhere super close since it's not something you can necessarily find everywhere.
But I highly recommend it if you can find it; it is something a carnivorous fish would naturally eat, which is one of the reasons some people aren't crazy about feeding peas. They are super tiny and look like dust! I just feed a small pinch with tweezers, and then I use one of those baby snot sucker things to suck up what she doesn't eat in one or two bites.