I have a client that I have to rebuild their pond due to a drunk driver , yup its first for me lol. The car went right through the back of the house and into their pond. Guess it was a good thing the pond was there or it would've went through another house in their backyard. I got replace everything but my question are about the existing rocks due tor the fact fish will be replaced as well. Do I need to replace them as well due to fact that radiator fluid, oil, tranny fluid, brake fluid etc was leaking and present in the pond. Due to porous nature of stone I know there is residue left. Can I power washer them with a bleach solution or degresser solvent? Or will a soapy solution work fine? Or is it not enough that's worth worrying bout as long as I do so stone washing and add charcoal /carbon to help neutralize the contaminents . Again I've never had a car in the pond so this is a first for me.