you need to keep the ammount of rotifers in the tank high enough so that a newly hatched clown can see one within a body length, do you know how many rotifers that will take to fill a 55 gal? the rotifets will most likely fit through that filter pad and not stay where you want them.
I understand you said you will have it seperated but the fry will get cought in the filter pad that you have covering the 3-4" hole and basically die, they will find every nook and cranny they can. also the small hole you will use to blow fresh water into the divider better be very small as fry are about 2-3mm long.
all in all it is a bad idea to try and raise the fry in the parent tank when all you need is a 10 gal tank, air pump, small heater, and bubble wand to raise clowns.