I personally hate freaking guppy, platy, and molly. Swordtail on the other hand I kinda like, nothing I'd dedicate a whole tank to. I would just keep nanos, or JD fry with the Swordtails and use them as a dither fish/ money help, never hurts to have a small little income for food. I wouldn't be taking any extra special care of them, I mean there so boring. You can go and get a bag of feeder fish throw them in the tank and get the same if not better entertainment! HAHAHA