HELP!!! What The Hell Is This Stuff???

[untamed]

Originally Posted by MMAX

Today I dismantled the whole set-up. Every rock was taken out and scrubbed, the back glass which was also grown over with the stuff was scraped, a bunch of the sand which had collected a pile of it was chucked and finally a 90% water change was done.

What are you using to provide biological filtration on this system? If it was the rocks, you have potential problem there because you would have destroyed your bio filter when you scubbed all your rocks....