I use my own concoction. Generally it is what everI feel like picking up from the fish market, saltwater stuff of cource. Usually shrimp, clams, fish, squid, etc. I also add some nori I get from an oriental grocery store, unseasoned. I take about half of what I get and blend it to a liquid. I add the rest and blend it a litte so it is chunky. This I freeze the whole mess in a shallow baking pan. I make a couple of quart sized ziploc bags at a time and it last for a while.