Reading again this morning, sorry if my response was harsh. Hang out here for a while and you will see that some people post these types of questions just to be rude. I would never expect that from you, which is what got my blood boiling a bit. Again, my apologies.
Now, back to the question. I have seen some applications of undergravel filters modified for other purposes. Purposes which I personally disagree with, but at least that make the question a little more reasonable. Were you reading on plenum systems? Or was this just one of those brain dead moments? Hey, it happens. For about 10 seconds last Saturday I thought that Louisville might upset Kentucky in Rupp Arena. Yeah. Duh, brain dead.