Under 2" and they will need feeding, over 2" and they will generally be self sufficient with the occasional light phyto addition to the tank for that added "boost". If under 2", the best means of feeding them is via a bowl outside the tank. Add just enough phyto to the bowl to give it a weak jade color. Add the clam and after about ½ hr or so the water should be clear for the most part. The bottle idea does work as well but you run the risk of clogging the clams gills if not extra careful. Aside from that, you do not introduce unneccessary nutrient to the tank with the bowl.
As for the anemone, be extra sure you run carbon in the filtration at all times. Clams are somewhat sensitive to toxins and anemones are among the worst. I would also suggest adding the anemone first. Once it's settled and established the clam placement will be easier and not subject to the wanderings of a new anemone.
"Ideally" though, anemones are not technically reef creatures. The best situation is one or the other, not both. Not being a perfect world though... 8)
Cheers
Steve
