I recently bought a bag of “black polished river pebbles” from Home Depot that I want to use in a new setup. When I opened the bag they feel kind of waxy. No where on the bag does it say toxic or not safe for aquariums it there is a label stating “improved with sunshield (tm)”. Anyone k ow what sunshield is? I was going to boil the rocks but would like to know if there is anything toxic about the coating. It’s supposed to protect from fading in sun. Should have avoided these . 
