There is something to when a fish is added to a community. This is most obvious in marine aquariums, where once the tank is started on its cycle (and at least until new fish are added, nitrites and ammonia are zero) it is good to add quieter personalities first. Some will add progressively larger fishes as time goes along. And yet there are some damsel fish individuals which can't be kept with anyone!

Raising a number of species from fry will allow them to sort out their pecking order before they are too large to do great damage or corner compatriots nearby. Separate those fish and put them back together and watch the scales fly!

Once ambled into an Indianapolis living room and beheld a 20-gallon aquarium with six adult male Bettas. Putting them together is a supreme no-no! But the females (and their pheromones) were removed and the male Bettas allowed to grow up together. Their fins weren't perfect, but that was an awesome scene.

Somebody else (years ago in a local aquarium club publication) actually did an experiment with such a community. They removed a male Betta for a minute and returned him. Nothing happened, the pecking order was still recalled. The experimenter progressively increased the time a male was removed and peace remained. Around 10-15 minutes the Bettas had forgotten who their removed compatriot was and boy did fins flare! The aquarist had to get that boy out of there permanently!

kimij67 noted how different the personalities of her guppies are. You need to watch those fish if you put them together. The first of a couple of guppygirls here (the superuser) put a magnificent large male swordtail in her community tank, which I sort of recall being larger than yours. It killed its mate and terrorized the guppies. (You idea of trios is especially wise in the case of swords, though a small group of unsexed swords might work even better.) Some fish in guppygirl's tank were so bullied that they lost their immunity to the local critters and 4-5 were lost to Hexamita. Bullies can be a major source of stress and consequently disease. She was sad but almost glad when he jumped out of the tank.

Oh yes! They are gifted jumpers. Cover the tank as tightly as you can. Maybe plastic (or temporarily cardboard) can be shaped and taped around - but not touching - heaters and filter outflows. If you have one of those hoods which can be altered to fit closely, only carefully cut away bits of the hood.

Another guppygirl requested more on breeding swordtails. In response, a Breeding Livebearers "Walkthrough," especially dealing with swordtails, was posted. That is in Immediate Help and may offer a couple other insights on swordtails.

Though it is uncomfortable to think about, you may want to consider what you will do if despite your best efforts, your male swordtail is really, really aggressive. And you think, "He wasn't like that in the shop!". Sometimes even watching their behavior there isn't enough, though it can really help.

Will the shop take the swordtails back or trade a bigger male back for a smaller one? Would you have a place to take the bully or bullied fish if you kept them? (I once put a male swordtail in a tank of larger and rougher fish. He got less pushy fast! It did carry over a little when he was returned to his original quarters.) Is there a friend or neighbor who has an aquarium and can house refugees?

Swordtails do need space. Mine have done their best when in 20s or even 55s. Mine have not grown as large in smaller aquariums. (Go figure.) And you should see a male go into his mating dance/display in a larger aquarium! He is all over the place!