There is actually some debate over whether or not corals will consume phytoplankton, some of the experts who drift into the scientific forums elsewhere have suggested that corals flourish under phyto dosing because they are consuming the eventual boost in zooplankton (ie. pods) population. Not so much because they are eating the phyto. There was some suggestion that corals lacking nematocysts (though the proper genuses elude me) may be phyto consumers as phyto doesn't need to be effectively speared in order to eat it. I may have gotten that wrong though..
Honestly, if you are feeding filter feeders like sponge, feather dusters and perhaps clams (though dont quote me here!) I would not worry about the type of phytoplankton you use. Nannochloropsis and Tetraselmis are nearly fool proof, easy to culture, easy to come by (I may have a culture you can play with!), and are fine for raising pods and the other indiscriminate feeders. Now, would you get more pods if you used more nutritionally packed phyto? Perhaps.
When you jump into rearing larval critters, or need to enrich Artemia (BBS) and/or rotifers for feeding out further up the food web to your desirable organisms, then its time to really needle about which phyto's are best and what mix is best. The guru's in the breeding forum here on RC would be ideal to discuss this at length and the differences in quality between say Tetraselmis, Chaetoceros, Pavlona, Thalassiosira, Isochrysis and others.
Why dont we need to hassle over feeding pods highly nutritious food? They seem to be able to manufacture plenty of HUFA's (those good fatty acids that keep fish in good health) on their own.
Three links I think you should read if you want to plunge headlong into details:
Growing phytoplanktons at home, by our Dr. Marini.
Culturing your own phytoplankton, from the old All Things Salty forum
How to avoid phyto crashes, a good Melev thread
>Sarah