I also have a bunch of asphalt in there from the Sound. It was dumped on Bar Beach over fifty years ago to control erosion. I also take the asphalt and collect the amphipods from it by swirling in a bucket of water then I put it back. Normally asphalt is very poisonous to sea life and I would not normally use it but since this was submerged for so long I tried it. I also had it tested by a testing company for toxins. Don't put asphalt in your tank, leave that for strange old reefers like me with experimental tanks.
For some reason it gets covered with coraline algae quicker than "real" rock. My reef is kind of a garbage dump biotope :bagfish:
Remember, no asphalt, beer cans or Oldsmobile transmissions.
Paul