I am far from a fish expert, but let us examine general animal behavior in nature. *
Generally speaking, males want to "plant their seed" as often as possible in order to ensure their genes will be passed on (essentially, continuing the proverbial family line). *The females will not re-enter estereus (get frisky *

) until all their children have reached an age where they can fend for themselves and are self sufficient, so it is to the males advantage to kill whatever prevents him from mating (most species do not recognize as a child as "theirs", it is mostly a primate/upper mammal thing). *Furethermore, if the age at which the fry become independant happens to be ten days, then the alpha male (aka daddy) will see the male spawn as competition for mates. *Adding another female into the mix might prevent him from devouring the fry because there is another available mate...of course then you will have twice the number of fry. *I would think your best bet is to remove him should they mate again...but like I said, I don't know all that much about fish.
Kevin