Cyclo-peeze comes frozen, or in a dry form. I prefer the frozen, but in a pinch I have used the freeze dried version. Did you look in the frozen food section of the LFS
Sure you can add mussels. I would rinse everything well just to make sure they aren't sprayed with any preservatives. Did you read through the entire thread I posted a link to? The one guy Rod mentioned Trylophosphate (and it seemed I was pretty hard on him...maybe we got into an argument prior....hmm...mildly embarrassing). Anyway, the idea is to use fresh ingredients and know exactly what's going in your tank.