Adding rocks?

I have purchased a filter and pump,which is happily bubbling away. I have some granite chips which I want to use to build a wall type shelter for fish to hide in. These were in a pile outside for the last year. I use them to build in my succulant garden. Are these safe to use in aquarium? How can they be cleaned? I still need a test kit before I buy more fish. Am I on my way or am I still missing something?

Granite should be safe. Wash em off.

For piling, I would reccomend buying aquarium silicone seal to glue the rocks together to avoid the possibility of a rockslide.

Will do. Thanks