I'll agree w/ Ed on 99%. Most fish that we can breed commonly will readily take "L" strain rotifers. If your trying something unique like a pelagic spawner (centropyge sp. , wrasse sp., etc) then maybe, just maybe something smaller is warrented. I've listed below the common sizes for rotifers.
large -L-300-350(microns)
small-S-180-220
super small-SS- 80-100
What i've found is that the "ss" strain is mythical at best. A number of folks have it, and it grows, but it always seems to be contaminated w/ S strain, meaning that its just a runted version of the s strain. I'm still awaiting to see, touch, and grow a consistant batch of "ss", that stays "ss"