Yeah, the swarm works its six million power and it still can't kill the Acutians faster than they can build them. Back when the armada power was lower, maybe a million, I helped them out by sabotaging all of the planetary ion cannons, all of the bomb shelters, and dropping the planet's Environment score to about -95. Still didn't matter: they didn't even make a dent in the population, and that Environmental score recovers quickly. Even when they went to the recently conquered world they couldn't do anything to slow their rate of growth.
Which is weird, because a few tens of thousands of fleet power were able to crush the Burlusts down to one million population and then leave, laughing the whole time. So if I kept that save (which I didn't, since I blew all my money on sabotage), I'd be at a point where the Thoraxians were wiped out by a Peltian fleet, the Peltians and Boarines were dropped to one million by plague, the Burlusts were dropped to one million by a diversionary fleet, and the Acutians survived the Grand Armada of the Federation without the benefit any defensive structures without even blinking.
EDIT: Forgot about the Thoraxians.