Well I am told (no personal experience) that given enough Light, they should be ok with that. with lower light levels, I have heard of people using an inverted 2 liter bottle w/the bottom cut off, and a peice of air line fitted into the cap. basicly you submerge the bottle and place it over the clam. with a syringe shoot phytoplankton down the airline into the inverted bottle (a pre determined amount). the clam will feed until the water inside the bottle goes from cloudy to clear. I beieve I have heard ReefRunner discuss this method some time ago.