Advice on rocks Desperately. needed

[bookworm]

 I dont know what kind of rock this is,so i need to know that and also need to know if it is aquarium safe. I also have a piece of slate, that I soaked 24 hours how do I know when it is safe to use in a tank? 

[redmare]

You will almost certainly be fine as long as you’ve somewhat cleaned it. I’ve used so many different rocks in my tanks that I found outside, cleaned with literally just water, and put in. Slate is absolutely fine! I believe if you pour a little vinegar on a rock and it bubbles, then it’s a softer rock that will technically slowly dissolve in your tank and raise hardness a little bit but if you’re doing anything close to regular water changes this won’t have a tangible effect.