you'll want a density somewhere around 15 rots/mL
you can add phyto to the larva tank to keep the rotifers present in the larva tank fed, and reproducing. you'll want to test your phyto to see if it's full of nitrates from the fertilizer still, tho...the instances where i have fed phyto to a larval tank (I typically only do this when the hatch is delayed a night beyond what it normally should have been - such fry will have went thru more of their egg sack..making sure every rot they eat has nutrients is a plus) i just strained the phyto thru a couple of coffee filters, then scraped the green goo that the filters collected into a cup of water from the larval tank. stir/agitate the crap out of that to 'disolve' the phyto back into the water. that way, you aren't carrying any of the nitrates from the phyto culture into your larval tank.
those that are more experienced with it may have better tricks to doing the above, tho...i only do it if i have to. seems to make the tank too volatile, and i end up doing 3 to 4 water changes per day. of course, i'm only doing it with clutches that are already a little behind anyway, so that could factor into it.
i know the feeling man...there's eggs there, and you want to raise them...but unless you are ordering a rather large (6-8 liters) quantity of rots, you would probably do better to let this clutch pass and concentrate on getting your phyto/rot cultures up to snuff for the next batch....especially if this is your pairs first spawn. seems like more often than not, a females first clutch will be a little wonky (fry that can't detach from their egg casing completely, low hatch rate, etc). that said...if they've started spawning, they'll most likely keep at it unless you disturb them, or their tank parms go wonky.
if you haven't already...seek out "Clownfishes" by Joyce Wilkerson - it's got a treasure trove of info in it for what you're wanting to do.