WOW, really
adding that much phyto can really compramise water quality, I dont think they need to eat that much. I add 2 drops of phyto in my 125 gal once every week or two. and I have allot of filter feeders. the clams will get the nutrience they need from the photosinthetic (spelling) algie in their body and the lighting you provide for them. I would only add phyto if you feel the lighting isnt strong enough, then you can suppliment with phyto.