+1, I really could not agree more. What SDS is talking about with the algae in the clam mantles is a symbiotic relationship with this algae (zooxanthellae) in which intense lighting feeds the algae which in turn feeds the clam. IMO you will need a minimum of T5 HO lighting, with MH being the preferred option, for keeping any clam. Also, SDS hit the nail on the head when he said that clams need an established tank. The reason for this is that in addition to the nutrients they get from their symbiotic relationship with zooxanthellae in their tissues, they are filter feeders that feed directly from the water column. Plus, for a marine tank, it takes much longer to be considered "established" than a Freshwater tank would; meaning, you cannot count on stable water parameters for AT LEAST several months after setup. Marine invertebrates are not tolerant of wonky parameters for the most part.sirdarksol said:Saltwater clams should not go without salt at all. It's extremely bad for their cells. Most saltwater clams also get pretty big, and need large, well-established tanks to survive. Even if you had a saltwater tank, it would have to be set up for six months or longer for the clam to have a chance of survival. Further, most saltwater clams have algae colonies in their mantles, and need a lot of light to support these. In other words, they're often more difficult to keep than corals.
I'm gathering, from a number of your posts, that you want to set up a saltwater aquarium. I'm going to further guess (feel free to correct me if I'm wrong) that you may already have a saltwater critter, perhaps something you picked up during a trip to the beach. If so, I would strongly suggest taking it back (to the store if you bought it, to the beach if you picked it up there).
From there, I would very strongly suggest doing some research and learning about how to set up a saltwater aquarium. It is an expensive task, and requires a bit more attention than freshwater, as you've got to keep a closer eye on mineral concentrations. Once you have one set up, then start thinking about stocking it.