Yep, I agree with Kristy, sandstone/limestone has to go asap and don't worry about the cyano, your tank is only a few months old, so it is still cycling anyway. Don't rush it. The purpose of LR is more than just for looks. Deep in the rock, live very small animals that will help cycle your tank and create a unique natural filter system of their own. Shot, finding out what is hiding in there is half the fun.