hey hope its not too late and that i can help... my banggai just had 18-20 babies. i moved mine to a spare 20 gallon that i had laying around on day 20. i moved some of my rock over for him and put a hob
skimmer it too that i had laying around. while thats not the same as your sump its what i had so i went with it.
he released the fry on week 4, same day we added a long spine urchin to the tank. the owner of the lfs
suggested the newly hatched brine too. he should know he used to raise them years ago. any way. i wasnt set up for that bit BUT i did have nutrimar ova. if your not familiar with it you can google for in depth info but its frozen prawn eggs.
the babies have been eating that, fortunately for me, from the time they where born to now.. like a week later almost. they where 1/8" long, give or take, when they became free swimming and now some are 1/2" some are 3/8" so i know they are growing. ive seen them eat it so im comfortable with saying its a great alternative to newly hatched brine.
hope that helps. fyi this is the first time i have ever dealt with banggais spawning so its all new to me. just passing along whats going on with mine.