Yellow Encrusting Sponge. I have to do more research what kind it is. As of right now, it is super hardy like the red knob encrusting sponge. The best description is that it looks like a couple of small ball sponges which are smaller but it is spreading like a carpet. We will probably sell them in the size comparison of the diameter of a baseball. I don’t have a picture yet but it should not stop you from buying this addition to our website.