I was buying littleneck clams from the gorcery store for my CBB when it was first introduced. I would keep them in the sump, as somehow they were still alive on ice when purchased. After a bit, I would lose 1-2 here or there, as they would bury in the sand. I just kept getting 3-4 every time I would go to the store. Lose 1 or so, find 1 that was from before and repeat. I no longer feed the cbb clams on the half shell, as it eats my DIY frozen food, which has clam strips in it.
Needless to say, I now have 5 in my 180 display and 4-5 in my sump lol. They move around the sand and the only hint they are there are their necks just barely sticking out of the sand lol. Being as they move around, them and my decorated goby keep it pretty clean. I have had them spawn once, but it was nothing like if snails or anemones spawned. Much lighter "cloudiness" and the corals seemed to love it.
Funny thing on little necks, is that they eat cyano, diatoms and dinos. I have never had issues with those things above the sand bed, but always some have been present below the sand where it meets the glass. That has been reduced to about nothing since moving them to the DT. There is still some here or there, but not near as much.
