It's best to keep two female to each male as they will pick a mate and breed faster with twofemales. One thing you must know about blue acara's are they breed for live. Once they choose a mate they will bred only with that mate. So it's best to keep two female let the male pick his mate then remove the one that isn't chosed.
I keep the red flag acara and the dwarf flag acara they are also the same way.