Sump question

[velezdav]

I have some (slime) on the top of my water by mi first chamber of my sump also saw several things on the bottom my tank been up for 6 month and doing good , also i have rock that i had from when i got my tank that i didn't use ( was live rock from previous owner) i pressure wash and left it on my garage dry , i starter my tank with dry rock , would it be safe to add some of this rock or should i get some dry .... Thanks