first thing first, with 3 females you are not only going to be over run, it is going to happen kind of fast. if you are interested in not inter breeding, you might consider getting a few more 10g tanks. every 30 to 35 days give or take a few, each one of those 3 females is going to have anywhere between 20, and 100+ each month. find friends, family etc, anyone you can to take the fry you dont want, and even consider having a couple of fish that will predate the fry to keep the numbers in check.