Not necessarily...
I had a tank with cork panels inside the back glass. I had read all sorts of books and websites that said it was a perfectly safe material to use in tanks, but all my fish died one by one. Eventually the tank started to smell funky, and I realized something noxious must be coming from the cork - it took almost six months for the fish to start succumbing to whatever chemical it was releasing.
Keep doing research, keep an eye on your fish, and make SURE it's safe.