I've done both methods (used tulle instead of screen though). IMHO, the sponges are better not only for anemones but fish too. I lost a kole tang to a PH b/c my sponge pre- filter fell off. I believe the sponge would of gave him a chance and the tulle would of still let the tang be stuck (though tulle has saved a few anemones before I added the sponges). There is just more of a "buffer element" with the sponges, IMO.