Some claim that small clams need spot feeding but I don't agree. If you feel you need to feed them then I recommend feeding the whole tank a quality live phytoplankton.
Tom
+1 on the phyto! You need to be really careful spot feeding something that is to big (particle size) will clog the clams gills and then it wont be able to breathe.
"The beatings will continue until morale improves."