You're not wrong, there has been some bickering between the angels and him, but since there's not too much size discrepancy (yet!), and the tank has 4ft of swimming space, they are cohabiting ok. I've got a 300 litre in the garage that I'm setting up, and 8 other tanks running, so if needs must I can quickly change things around... I also have a menagerie of other empty tanks in the garage.
I have a big female that grew at a similar rate to my oscar, so you're quite right in them being time-bombs!