Encouraging fry to eat other than from (parent)

[Miffy moo]

My fry are now 10 days old I am trying to encourage them to eat BBS but not really interested. I have been squirting them via a syringe onto dads side. They only have dad to feed of as dad was a very abusive partner to mum so they had to be separated! He really got stuck into her. They are in a five foot tank partitioned off with a divider. It is actually a community tank, i really didnt expect fry to get this far. I am doing 50% water change twice weekly is this enough? Considering the volume of the tank. What size should fry be at the moment? Sorry for all the newbie questions I just want to do the right thing by them. I could move dad and fry into a 70 litre with a major rearrangement. Any help greatly appreciated.

[ILLUSN]

keep up the bbs, by 14 days they should be onto that, keep an eye on the fry if their bellies turn orange you know they are eating the bbs, once they get used to it you can remove dad and just raise the fry on bbs and a good beefheart mix

[Miffy moo]

Thanks illusion, really appreciate your advice :D