There are many types of clams available for the home aquarium. While they may look very differnt both in shell shape and color they share general care requirements.
All clams require a stable alkalinity at 10-12 dkh. Calcium needs to be maintained at 380 ppm or greater to ensure consistent growth. Contrary to popular belief Tropics has found that aquariums that tend to be under skimmed, ususally with higher nitrates 30-50ppm tend to produce bigger, healthier clams. Clams are not as sensitive to temperature as many other corals and inverts; a stable temperature of 78 degrees is fine. It is very important to maintain alkalinity with clams. If calcium gets to low it will reduce growth and in the long term will cause shell deterioration. If the alkalinity falls into the low 6 range, clams will die without warning. Tropics refers to clams as canaries in the coal mine when it comes to alkalinity in the aquarium.
Special care note: when clams are less then 2.5″ front to back it is vital to feed them. What you choose to feed is not as important as the feeding itself. Cyclops, baby brine shrimp, phytoplanton, oyster eggs, are all exceptable food choices. When clams are small they rely on the nutrients they get from the water column. The home aquarium does not have enough water rich in nutrients to support the smaller clams; this is why they need to fed at least three times a week. When clams hit about the 2.5″ size they are able to do without the constant feeding. At that point they use light more than nutrients for growth and health.