Salt.

[Fredyyanez]

An I add this "rock " that I got from puerto Rico to my fresh water 10g tank? It taste salty and I was wondering if it would be detrimental to my fish. It's been out of water for 8 months.

 

[Alyxx]

First test it with some vinegar, or even better a strong acid (if you can get some) to see if it fizzes. If it does it will affect your ph so you don't want to add it to a tank. Fizzing means it will raise your ph. If it doesn't I would soak it in water for a week or two, changing the water as often as you can. Use very hot or boiling water when you change it. After a week or two, maybe take a sample of the water it has been sitting in to your LFS to see if they can test it with a refractometer. If they carry saltwater fish they should have one and be willing to test it,