[coral reefer]

Tridacna Clams require very fine nano /phytoplankton and yeast for food while in the baby-juvenille stages of their life so light really isn't a concern right now! The problem is feeding clams at that small stage in life because they will not eat most of the food(liquid/frozen/live) that we offer our livestock. The reason why lighting is of little importance right now with clams under 3" in size is that their iridophores and zooxanthellae have not developed for photosynthesis and that whole process.
Tridacna clams also require nitrates, phosphtaes and ammonia believe it or not for their success over the long term!!!!!
IMO, I would shy away from these small clams and go with a bigger clam and ORA(farm raised ones will fair much better than wild caught clams) ones are the best.
The Durasa and Squamosa clams are the least light dependent and hardier of all the clams. The Maxima and Crocea are at the other end of the spectrum, with the Gigas and Hippopus in the middle. Durasa and Gigas clams will reach over 2 feet in size and weigh over 100lbs so take that into consideration to be able to deal with that when the time arises.
Maxima and crocea are rock boring clams and should be placed in your rock work whereas the other clams should be placed on the substrate(benthic area of your tank...
Hope this helps-short and sweet!!!!...