I got some rock from a freind of mine, a while back. Rock was 10 years old, in a higher nutrient tank. Rock was pretty loaded with nutrients by the time I got it, and was growing all kinds of algea......
Heres a thread that covers alot of what I did, but not all. I will update the thread soon. I will give ya some time to absorb all that is in it, and then post the outcome.
Sounds like cooking the rock, or selling it off and replacing it, are your best bet- depending on what you are able to do easiest. Just follow the direction perfectly, unlike I did...if you plan on cooking it.