I have some small rocks that my sister gave me. She collected them from a lake we go to in the summer. I know there are some petosky stones and quartz, but don't know what types the others are, but shape-wise they seem great for an aquarium (no rough edges, etc.). I'll do the thing where you soak them in water and then test the water to make sure they're not giving off unwanted chemicals / minerals.
Here's my question, meanwhile: my sister coated them in polyurethane so that they'd look wet and show off the coloration. Is that chemically stable enough to go into an aquarium with my betta (and corys and possible future neon tetras)?
Thanks for any advice you have!