When I first found those things in my 180 aggressive tank's sump I took a few out to examined them and took photos. After I cut it open I was like 'uh-oh'... )
If it's used for the education in school, you may get a free piece with live rock attached if you can pick up from my home tank at Great Neck, or wait until 01/18/08 by attending LIRA next monthly meeting which will be hold at my office at Commack.
I also have an used 175G 6 feet Oceanic black bowfront tank with matching stand, 6' 150W MH/PC lighting, live rocks, some corals and fish, and other equipments which can be donated to the school if they have the fund, people and plan to support the long term maintenance.