Vinegar and Rocks?

[monster]

Good day fellow froggers, hope everyone and there frogs are having a good start to the day. I have a quick question I was wondering if someone could explain to me. So I was reading in a post for FBT's something about a vinegar test on rocks. I have never heard about this, I just started keeping frogs in august and have tried to educate myself on the spieces I have and also others as much as possible. But I haven't came across this vinegar thing yet, could someone educate me please and thank you. And I hope I put this thread in the right spot. And im very curious about this because I have variety of different kinds of rocks I my FBT enclosure in the water and if there is something in there making them sick I have to get it out.