Make a splash with tank decor your fishy friends. Plants provide a lush, natural environment while also providing hiding, resting and nesting areas. Ornaments, from pirate booty to the Brooklyn Bridge, help your fish think outside the tank. Set a scene with richly hued driftwood. Rock decor mimics the aquatic landscape found deep under the sea. Decorative gravel, in a range of colors from bright purple to lime green, really pops. Substrate helps provide the right chemical balance for your undersea world. Look for types that stabilize not only calcium but also alkalinity.