OK all so heres the situation a few yrs ago i was gone on vacation and while i was gone my PBT got some ick and my mother decided to treat it on her own she went out and bought something Now i say something because she didnt remember what she used and i couldnt find anything that was empty so i have no idea what she used but she only dosed it once and the ick was killed and has been gone for years, now i have since tried to put a sally lightfoot in the tank from one of my other tanks because it was getting too big and after a week id say it died mystertriously. so it got me thinking what if the product my mother used had copper in it and now the rock has absorbed this copper and now i cant put any invertibrates or corals in this tank because of the copper. but in the tank in question there are a few snails that live just fine this whole time and i have lots of sand worms and brittles and everything so it got me thinking does copper only kill crabs? and are snails inaffected?. also another thing i have taken a few rocks out of the tnak in question and put them into my reef tank over a yr ago and i have corals and crabs and evertthing in that tank basically and i dont see any adverse affects to any of them so i was wonderibg if there is a copper test that would be able to read the slightest amount of copper in my tank water? because now all the copper would be absrobed into my rock. maybe i can test the rock sumhow? Also is the rock that is in the tank now not good to be used in a reef?well any feedback is appreciated