Polished rocks?

[Blue Eternity]

Today, while browsing the dollar store, I saw some rocks that I thought would look fabulous in the new 10 gallon I'm planning on setting up for my two boys.

However, when I got home, I noticed they were labeled as "polished". Will these be okay? I boiled them and a sort of film formed on the top of the water (looked kind of like oil). I dunno if I trust putting them in the water or not.

Could they hurt my fish? If they could, where can I get some medium sized (like 3/4"-3") natural looking river stones?

thanks!

[dramaqueen]

Those rocks could be leaching out something. I don't know if I would trust them or not.

[Blue Eternity]

I'm going to try sanding the rocks, and boiling them again. If they leech anything still, I'm going to try boiling them until they don't leech anything. If it doesn't work then, I'll need to buy different rocks.

Does anyone know any places that sell natural river rocks? (enough to cover a 10 gallon)

EDIT : I just read that polished rocks are okay, although that was about rocks polished with sand and wearing down. I'm going to boil them just in case. :]