Oh, sorry :)
The vinegar test is how a lot of people test stones before putting them into the tank. If the rocks fizz when the vinegar touches them, they can't be put in with the fish, but if they are non-reactive, they are safe.
I wish I had a better explanation of how this works, but I don't :/
EDIT: Now that I'm googling it, I'm seeing a lot of people saying the vinegar test is unreliable. I've got mixed stones outside my sliding glass doors and have them in 2 of my tanks with no problem, but as they are mixed, I thought it safer to test them first...
Everyone is saying to soak the stones and test the water parameters, but I do not have a testing kit...
Any other methods that you know of?
Last edited by toad; 10-01-2012 at 08:17 PM.