He's just doing what males do,if he were a dog a swift visit to the vets would be in order.
You could put in a fry net to seperate him from them for a while,might make him worse though lol
If it's one pregnant female he's chasing and not the other you could move her for a while into the other tank(in your sig) and net the baby you have if it's still to small.May turn his attenton to the other more which may in turn even it out when all reunited again.
Putting in more decor/plants if you haven't already so the females have a place to hide.
If you aren't keen on having them breed then rehome the females and just keep/buy males for your tank in future.Keeping females isn't good for live bearers as you may buy them pregnant.