What species of fish is it that eats the father? I've never heard of that before.
Betta channoides are mouthbrooders. The female passes the eggs to the male and he holds them in his mouth for around 10-14 days and doesn't eat at all during this period.
When the fry are released, they are slightly larger and more developed than fry from bubblenesters (such as Betta splendens). The male will usually spend a few days looking after his fry and then they will go off and do their own thing.
It's quite interesting, particularly when you see the fry moving around in his full mouth.