Also, I'll probably be doing Java Ferns and Anubias to start since goldfish (supposedly) won't mow them down in 30 seconds. Do they have to be attached to rocks or driftwood, or can they be put in terra cotta pots with gravel? Would they need some kind of smaller substrate (like sand) or something even more specialized? And if they do need attaching, can I just tie them to a relatively large rock (fist-sized or so) instead of wood (which I've heard can mess with PH if not handled carefully)?