3" clam feeding myth busted
3" clam feeding myth busted
http://www.advancedaquarist.com/2010/7/inverts
The "Three Inch" Myth
I have read and been told at some time or another that all tridacnids must be fed phytoplankton for long-term survival. Obviously, this is utter nonsense. However, much more frequently, hobbyists bring up the "three inch" rule, which sounds much more reasonable, but is also nonsense. So, let me kill this one off, too.
For several years I've heard that any tridacnids under about 3" in length must be fed regularly or they'll starve to death. The supposed twist here is that mature tridacnids can get all the C/E they need from their zooxanthellae, but immature clams cannot do so because they don't yet harbor enough zooxanthellae in their mantles. The story goes that when young it takes them several years to build up a full complement of zooxanthellae, and that they must get the rest of what they need by filter-feeding until this happens.
I could go into great detail as to why this false, but I'll keep it short since I already did that in my book. The fact is, small tridacnids, just a few weeks old, have all the zooxanthellae they need in order to thrive, and this population keeps up just fine as a clam grows, too. One study above all others bore this out. In a controlled experiment,
Fitt & Trench (1981) produced several larval specimens of Tridacna squamosa from sperm and egg, and then reared them for 10 months. These juvenile clams were kept in a flow-through system and provided with filtered seawater for the entire time, having no access to planktonic/particulate matter with the exception of being given some zooxanthellae early on in order to get their population started. For the duration of the experiment the clams not only stayed alive, but grew. Of course, the filtered water did contain dissolved nutrients, which the specimens could readily absorb, and that should be plenty enough to quell any arguments about juveniles requiring additions of plankton for survival.
