silica

[MKCindy]

I have some old rock that came with the tank, some looks like coral and some I'm not sure of. (the guy ran and salt and a fresh water tank) I plan to break it up for the refuge tank.
I remember some one mentioned a way to make sure your rock doesn't have silica in it. Was it test with vinager?

[LoneStar]

Yup its vinegar. The vinegar will disolve calcium carbonate (thats why its prefered in cleaning tanks :) ). So if its silica based, it shouldn't have any type of reaction.

[MKCindy]

Thanks. It fizzed big time.