I believe there's a test where you pour vinegar on the rocks and if it fizzes or bubbles it's unsafe and if it doesn't it's safe. I remember seeing it somewhere on google.
I've seen this test mentioned before, unfortunately it will not indicate if a rock is aquarium safe. Limestone (calcium carbonate) will fizz in vinegar and is perfectly safe on its own. It's the trace minerals to worry about.MJCanAm said:I believe there's a test where you pour vinegar on the rocks and if it fizzes or bubbles it's unsafe and if it doesn't it's safe. I remember seeing it somewhere on google.
I also would put them in my tank, we just can't guarantee anything from those pictures. A close up (as close as you can get in focus and dry) may give a more definitive rock id thoughDJRansome said:I would put them in my tank...but IDK what they are either. I did not have the impression of crystals (vision issue?), but what came to mind was after cleaning algae some remains in the tiny pits of the rock and then looks white when submerged for a while.