I agree with what others have said. The female is guarding the eggs closely, while the male protects their entire "territory". When my cacs had eggs, then fry they claimed about 2/3 of the 20 gal long tank, with the male all over this space. He never bothered with a guppy I had in there as the guppy stayed at the top of the tank. But he would chase the rams in there to the back corner and even go looking for them to make sure they stayed away.
Wow, your Cacs were much more aggressive than mine. I had GBRs in the same tank with them and the GBRs bullied the hell out of the Cacs until they eventually died. ;/ I only caught them a couple of times, but by the time I noticed, they were pretty far gone.