Live rock is never know good, if your getting the pink and green thats a good sign. What it is is coralline algea, not a bad type of algea. It encrusts everything that it can get a hold of. When it forms on the rocks, power filters, etc. the bad algea wont be able to grow on the spot that the coralline algea is growing on. You can never go wrong with buying more live rock. Live rock will filter your water for you, the more you have the better. They say you should have 1-1 1/2lbs of live rock per gallon. You can keep the inverts in. I was never a fan of the hermit crabs for the reason is that they would eat my snails. So to clean up the tank and extra food or what ever would be in the tank, I have 2-serpaent stars to do the job.