ok, since noone answered the why no plankton question, here ya go, I'm using an example I thought of yesterday.
plankton is great food for fish that can eat it. Seahorses have NO stomache; therefore, they need to beable to take out as much as they can from the food, as fast as they can. Plankton is not made up of things that are fatty;not as nutritious as mysis. Off the top of my head, I don't know whats in 'plankton' do you? Copepods are good, but if its chopped krill.. Ijust dunno whats in it exactly.
now, Brine shrimp is HORRIBLE. When I think of plankton, I think of BS... and The way I defend the no-using BS is this way:
Mammal babies drink milk. They grow on milk, then transfer over to solid foods. A mammal cannot go back to living on milk alone... not even with vitamin supplementation. NOW, that same mammal CAN live off of steak (or grass, i suppose) with vitamin supplementation;ever notice how your dogs eats grass???
milk=brine, steak=mysis.