The smooth giant clam (Tridacna derasa)Of all the Tridacna spp. clams available to hobbyists, perhaps the hardiest and easiest to maintain of them all is Tridacna derasa, the so-called smooth giant clam. This species is so smooth, in fact, that amorous, gold-chain-wearing male specimens have been overhead in bars making comments like, “Say, did it hurt when you fell from heaven?” and “If I could rearrange the alphabet, I’d put ‘U’ and ‘I’ together.” Okay, maybe T. derasa isn’t that kind of smooth, but its shell does lack pronounced ridges or scutes, making it relatively smooth to the touch. So, that’s probably where the name actually came from (though you have to admit my explanation is much more fun). It’s a fast-growing species when given proper conditions and a great choice for first-time clam keepers who have the tank space to spare.Physical traits T. derasa is the second largest of the Tridacna clams, potentially reaching 18 inches to upwards of 2 feet in length.