You can test if a rock is "inert" by placing a couple of drops of hydrochloric acid on it and seeing if there is a reaction. Some people say you can do the same with vinegar, but it really isn't acidic enough to work.
Hydrochloric acid is readily available from swimming pool shops, of course you need to be careful with it though
Any rocks you place in your aquarium should be washed well... I would recommend boiling them in a pot of water to help sterlise them.
Maybe you could post some photos if you find any nice rocks? I've been meaning to have a look around the beach here in Perth to see what I can find.
Hydrochloric acid is readily available from swimming pool shops, of course you need to be careful with it though
Any rocks you place in your aquarium should be washed well... I would recommend boiling them in a pot of water to help sterlise them.
Maybe you could post some photos if you find any nice rocks? I've been meaning to have a look around the beach here in Perth to see what I can find.
