I'm setting up a tank tonight, I found these rocks beside/in a local creek near my house. I'm going to clean and scrub them. Some of them i believe have calcium carbonate on them. I set a smaller stone in a jar of vinegar and it bubbled a little bit. If I add these to make some caves and hideouts, will it hurt my fish?

Tank will include: Bala shark Rainbow shark Betta Cory cats Bristlenose pleco Kuhli loaches Guppies Red rosy minnows Nerite Snails

I just want to make sire that the rocks won't break down and kill the entire tank. Also wanted to know, if I have fine gravel on the bottom of the tank, will these rocks sitting on top be ok in the tank? (Don't want the tank to shatter lol)