When I got my new fish, my dad (being cheap as usual) didn't want to pay for any of the rocks/gravel/sand at the pet store that we got him. We went to the dollar store and got these "accent stones". They're medium-sized smooth stones.
The problem is that when I was rinsing them before putting them in Donald's tank (2.5 gallon, unheated, unfiltered) it seemed like there was some kind of... stuff on them. I couldn't really feel anything, but the water seemed to just separate on the stones. I scratched the stone and there was a little streak where my nail had been. When I put them in the tank, there were little air bubbles attached to the rocks. You can see them here
Are they safe? Should I take them out? Is there anything I can do to make them safe? I haven't put them in my female's tank yet. I have no way to test the water.