I've been using eco-complete in my sorority tank with no ill effects to my cories. Their barbels have actually grown longer since I purchased them!
I've also had my plants thrive in eco-complete, too. When I don't kill them traveling >_<
I've also been debating adding some kind of fine gravel or sand layer on top, but haven't found one I've liked, yet. And even if I did it, I'll be saving it for the next time I move back to the dorms, as then I have an excuse to take everything out of the tank anyway xD