I've read many articles about the space needed for angelfish. Most recommend five gallons per fish. I suppose that means they need five gallons to get the right amount of oxygen. Because sometimes a sixty gallon aquarium can be too small for only six angels.
They very rarely hurt each other - I keep a constant eye on their fins and look for signs of nipping. But when the infants left for their new home last week and the infant tank was available, I moved the koi angels. Now they can try their luck at laying eggs and raising their young without fear of predators.
And now the blue angels have claimed one end of the sixty gallon tank while the blue marbles are at the other end. Peace at last!