I would not try it. You could get fry but I would rehome any males.
It is best to get younger females, but from what I have seen here on the forum, leaving a male in the tank can end up in disaster. Some members have had success with leaving a male in with the girls, yes. BUT, I have heard stories of sororities with one male in the tank that went OK for a year or so, then suddenly all the girls ganged up on the male and killed him, or other serious injury occurred.
You won't hear a lot of stories like that, but I think its because most members remove males when they find out that one or more of the fish is indeed male. They do that for obvious reasons.
A sorority, when established properly, can work out just fine, but it is my personal opinion that not removing males is not a properly established sorority. If you are open to rehoming males, it would be fine to let both sexes grow up together as fry. If you are also open to shipping them and have the necessary supplies, I don't think it would be difficult to find other members here who are willing to take the males.
I think that your tank plan so far sounds good. You have live plants and are establishing a cycle which is very important. I would make sure you have something to feed ammonia to the filter so the cycle you've started does not crash. If you've got ramshorn snails that came on your live plants, that would work. However, the filter itself if cycled that way will not be able to handle the bioload of 4-7 females added all at once. I would use pure ammonia or stock up on plants.
I still think that it would be best to purchase your girls from a breeder and not a pet store, but of course both will work. I just think that pet store girls will require longer QT time and will be more likely to get sick/already be sick. Breeder females will be in good care, will be more socialized, and by contrast, will probably be stronger and have stronger genetics than pet store girls.
I think that its pretty much impossible to over-plan a sorority. I do not think they are as complicated as people may make them sound BUT I do think its worth not taking extra risks. If that makes sense?
I would definitely get another girl to QT next to your current one to get them used to the presence of other fish. Something like VitaChem or IAL and very high quality food will help strengthen them up and boost their immune system. For the first two days, my sorority (with a filter and live plants) did not handle the sudden bioload and I saw ammonia and nitrites but I haven't since then. I test daily and will until I'm 100% sure the tank is keeping the water parameters perfect.
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