Happy as a Clam

The saying “happy as a clam” originated in the 1600s and was allegedly a phrase that sailors and shellfish collectors used. It was originally “Happy as a clam in the mud at high tide” or “happy as a clam in high water.” It was later shortened, and found its home in the vernacular of English speakers world wide, meaning: really, really happy. While we as scientists find it highly unlikely that clams are emotional at all, years of experience keeping Tridacna genus clams has helped us develop some husbandry tips to keep your clams thriving (and maybe happy?)

The general aquarium requirements for keeping most any clam are pretty familiar for most of you reading this article (assuming you are already keeping a reef tank). Temperatures should be between 78 and 82, and in our opinion, the lower end of this range is preferable. The pH range should rest between 8.1 and 8.4 and in both the temperature and the pH stability is incredibly important. Water flow should be turbulent and never laminar. The Mantle (pretty part) of clam can be quickly, and irreversibly damaged by a powerhead pointed directly at it. Damaged clams close up, and can actually starve themselves to death by not being able to siphon food or soak up light.

Most clams will do best in pretty intense, broad spectrum light. Some clams are more sensitive than others, T. gigas will need to be acclimated to very bright light, where T. crocea comes from shallower water and will generally require intense light from day one. Clams are one place where Metal Halide lighting still have relevance, though many hobbyists report having long term success with highest power LED lights as well. Metal Halides allow for deep water placement in a fairly broad area and since clams look best from above, you want them as deep as possible in the aquarium.

The biggest surprise / catch point for many aquarists is the water chemistry aspect of keeping clams. Even fairly small clams will drink calcium and alkalinty much faster than some of the most demanding coral. A few clams, or one big one will go through these elements fast enough to require supplementation above and beyond regular water changes. Not only can this be detrimental to health and growth of the clam, it can also impact pH and thus affect other aquarium inhabitants as well. Fear not however, as there are options for maintaining stability here; the easiest way to maintain adequate CA/Alk is likely 2 part supplements, though kalkwasser and calcium reactors are also options. Obviously a detailed testing regimen will be an important part of whatever dosing you choose to utilize.

We see feeding / nutrition as vital to clam health. There are many people who advocate for allowing the clams to subsist on the lighting and secondary food sources in the aquarium. A large portion of the nutrition needed by most Tridacna can be gained through their native zooxanthellae. However, they are all filter feeders and somewhat dependent on dissolved nutrients as well. This combination of needs means they do better in displays that have fish, as fish produce ammonia and particulate waste, both of which are utilized by the clams. Dense populations of fish work best as long as the fish numbers aren't overloading the filtration, and the fish are chosen to not pick on the clams. However, a truly “happy clam” happens through target feeding with Nutramar's blend of Live Micro Algae Products. We utilize these products in house and have had great success with clams we house long term feeding a regular regimen. We see more vibrant coloration and faster growth rates. This line of food has our highest recommendation.

Is your clam happy? Well, some species of clams grow at nearly unnoticable rates, and others can grow at more than 10mm per month. There can also be a huge variation in growth rates of clams from the same species, even in nearly (at least seemingly) identical conditions. Rate of growth isn't a good indicator of “happiness”. Look instead for a clam that stays open and extends its mantle well. Vibrant coloration is a good indicator that the lighting and nutrition are adequate. Clams should also be firmly attached, a clam that lets go of its own accord is likely very unhappy or damaged. As a side note on this point, clams should not be moved forcibly as the “feet” are easily damaged. To summarize, handle clams carefully (if at all), pay careful attention to water chemistry and it's stability (especially calcium and alkalinity) and make sure it gets enough light and food and you should be able to watch that gorgeous animal grow for years and years.