The limewood airstones are the best IMO for protien skimmers. They produce a much finer air bubble/mist than any of the other materials out there. They do however, have a short life. They clog very easily in saltwater applications. The salt and calcium deposits it will aquire will clog up the stone, rendering it useless, in a short period of time. Just keep them on hand, at all times. and replace them on a regular basis, and you will have no problems. I have to change mine every three to four weeks, but they are definately worth the money, and trouble. HTH
