Yep, plain seaweed is fine. Roasted is sometimes said to have extra sodium and iodine but I use it and never have had a problem with my cichlids or goldfish. Dried/roasted, whichever you can find - but possibly dried would be better. Here's the one I use: http://ninecooks.typepad.com/photos/uncategorized/2007/05/23/nori.jpg