You won't need bbs that soon. It takes up to 48 hours for them to hatch and then another one to two days for them to be free swimming. Personally I like to wait 3 days from free swimming to begin feeding anything other than what microorganisms were already in the tank.
I'm not entirely sure because I don't like to feed BBS until the fry are two weeks old. Personally I feel BBS are too big for fry but others feel differently. The day they're free swimming I would start your hatch and then feed the following day. Remember though that your going to have to start doing water changes immediately because the BBS at the bottom will go bad quite fast.
Well here's what I do after the fry are free swimming..
I add about 1/2 to 1 gallon of water a day (make sure you age it and heat it prior to adding it). Add it VERY slowly and try make too much of a current because the fry will get knocked around.
After several days your tank will be full. Begin siphoning off the water every day, it's up to you whether or not you suck stuff off the bottom. Some breeders say make sure you suck all the detritus off the bottom very early and some say wait until the fry are bigger to begin siphoning stuff off the bottom. The difference is if you wait the fry will be bigger and easier to see and therefore not suck up.
I would leave the fry in the 5 gallon for at least the first 2 weeks, even 3 or 4 depending on the size of the spawn. My last spawns have been very small so I kept them in the spawning tub for an entire month.