Rock identification - is this stuff reef safe?

[JDnKY]

I found this box of rocks at a lfs about an hour out of town. It came out of one of their freshwater display tanks. It looks like it could be coral but I’m not sure. I’ve bleached it in a 5 gallon bucket with a cup+ bleach twice now for at least 24 hours each time and soaked it in tap water with a cap full of Prime for over a week and changed water/prime 3 times. No smell of bleach at all now. There has been very little color change since I got it. There doesn’t appear to be any debris in it anywhere. It’s pretty light but doesn’t seem very porous. I don’t want to use it all but it’s mostly pretty flat and I could use a few shelves. These pictures are of the rock wet just after removing it from the rinse/soak. The back sides of the rock has a much smoother texture than the front.

Does anyone recognize this rock? Any thoughts on using it in a reef tank?

Thanks for any help!

 

[laverda]

It looks like volcanic rock which can contain all sorts of contaminates. Defiantly not ideal even if it does not.

 

[fish farmer]

I think that's what they call "lace rock". I can't help you on what the composition is. FWIW I used a few pieces years ago as frag rocks that I was mounting xenia and mushrooms to. I never noticed any problems with it.

 

[JDnKY]

Thanks for the input. I don’t know the history of this rock but knowing it was in a lfs freshwater display I’m sure it has been treated with copper at some point. Guess I’ll pass it on to my brothers-in-law for his 120 freshwater community tank.