I want to start a betta sorority in my twenty gallon tank that currently houses 3 (very young) platys, and one guppy. I know if I get docile females , the chances of them being okay with the guppy will be better.

But, I was kind of thinking I should start with one female, to see how the platys and the guppies react to having the betta in there before I bought the 4-6 more that I may add later.

But I've also heard trying to introduce more females into a tank that is already one female's territory can be a pain, so should I just get them all at once?

Yeah, I'd get 4-6 at the same time but also make sure they are already together at the pet shop. Pick 4-6 that don't seem to be aggressive. They should do fine with your 3 platties and guppy. Mine does fine with all my platties and guppies ...

It's a bad idea, sorry. You need to buy all 6 of your females at ONE TIME that way the sorority is already established and no fighting will occur.

Also, it's not recommended to house platys or guppies with any kind of betta, the colors and finnage will likely cause them to fight.

Why not just get a 5 or 10 gallon (10 would be better) and keep your betta sorority in there alone?

Veil tail betta, crowntail betta, orange sunshine guppies, 3 planted tanks.

its fine. bettas can go with any fish thats not agressive or has flowey fins

i fish keeper for over 6 years

Just get female betta of different colors.

I add mine weeks apart from each other and let them acclimate (float the cup/bag in the tank so they can see each other, remove water from the cup, throw the water away, and replace with tank water). I do this for about an hour and it allows the new fish to get used to the tank and water chemistry and the fish to observe each other. I've never had a problem with adding the betta weeks apart.

I have two cellophane , one solid blue, one blue with red fins, one pure white one, and one chocolate. They are in with guppies and oto cats. The ones that are similar color tend to chase each other sometimes, but leave the other fish that are not the same color alone for the most part. So my advice, get ones that look different. Timing doesn't matter as long as they are different enough in color and acclimated properly.