Are these rocks aquarium safe?

[superpeytonm]

I've been looking around the creek behind my house for a long time looking for rocks to stick in my aquariums. I found two that I really liked.
I poured vinegar over them multiple times and they didn't fizz, so I take that as a good sign. But I just want some opinions on if they'd be safe for aquariums.
And if they are, should I boil them? I've heard some rocks could explode if boiled.
Thanks for the help.

 

[Fishobsessed7]

I would think they'll be fine. Just scrub them very well. What you could do instead of boiling is bring some water to a boil and then pour the hot water over the rocks.


Fishobsessed7

Money Can't Buy Happiness, But It Can Buy Fish Which Is Pretty Much The Same Thing

 

[Delapool]

They look ok. I assume both are the same type of rock colour wise?

Let the vinegar sit in a hollow in the rock somewhere you think might react and come back after a minute to see if any slow bubbles. That would let the acid have a better chance.

If a piece of steel (like a kitchen fork except I didn't mention that) skates across the rock without leaving much mark it should be fine would be my thought.