Clam placement in the reef aquarium is often a hotly debated issue. Many people just shove clams into the sand, and for the most part the clams do fine. However, to present the clams with a more natural substrate, you must research the clam species you own and place them in the tank appropriately. Crocea and maxima clams are almost always found on hard, rocky substrates in shallower waters. Derasa, gigas, and squamosa clams are usually found on softer substrates and at greater depths. Your crocea might do fine down in the sand bed, but if your tank is too tall or your lights insufficient, it won’t thrive at the bottom of the tank.