Sponges

[Europhyllia]

Tebstan after some more reading I believe the thing the sponges get out of me feeding the tank is really the dissolved organics rather than the food items themselves.
"They absorb dissolved organic material from the water, but also need to have a source of bacterial or nanoplankton"
source: http://www.reefkeeping.com/issues/2005-07/rs/index.php
The excemption to this may be the filter feeder nutrient solution from Fauna Marin.
Thanks for asking such an excellent question about particle size.

I think the DT's I buy at your store has nanno in it which fits into that particle size
"Premium reef blend contains Nannochloropsis oculata, Phaeodactylum tricornutum and Chlorella with a cell size of 2 – 20 microns."