CaribSea Aragonite Dry Sands are great for new tanks or adding sand to currently established tanks. Florida Crushed Coral is ideal for very high-flow tanks with a lot of water movement that might blow other finer sands around and create bare spots. This grade of substrate is not recommended on its own for tanks with sand-dwelling or sand-sifting creatures, although it may be used effectively in combination with other finer substrates to fill in bare areas where current is concentrated.