Frag Rock Question Please

Hi,

I have a nice piece of rock which used to be in a freshwater tank but has been out of water and dry for years.

I was wondering if it would be okay to use this rock to make rubble to which I could attach frags. It seems to be quite porous. Do I need to worry about anything leeching out like iron or other metals? Or should I play it safe and just get some dead rock?

THanks

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