Hi. I like swordtails, platies, guppies but I have a bad time keeping them. They look good and after a month or so they die. Nitrites and nitrate are in check. The pH of city water is 7.8. I read that livebearers like it a bit harder. I confirmed that by my brother having Mollies that thrive and breed in his water. Which is a bit harder. I change water 7-10 days. The tank is 40 gals thats not overstocked at all. Swords are my favorite. If I can get them to breed I would be happy.