I got mine from Tidal Gardens aboutthree years ago and I love it, it's beautiful, easy to frag and has never shown up anywhere else in my tank or sump for that matter. To frag it, use scissors, cut as much off as you want , sell to your LFS. You can cut it up right in your tank, super easy (some sponges don't respond well to being out of the water). As for spreading elswhere in the tank...maybe they have a different variety than Tidal Gardens sells or maybe they have fish or crabs that bite off chunks, nothing in my tank has ever touched it. It adds great color to the display. If you should ever tire of it, take the rock out, rip off the sponge, use a knife or dental pick to get the last bits off or cover the bits with super glue.