Can Molly Live With Green swordtail?

Both fish want hard, alkaline water, and the overlap is comfortable: pH 7.5 to 8 at 24 to 28 °C. The question is temperament. Some swordtails and some mollies can be aggressive, unlike the placid platy, and here both are in one tank.

Size tips it further. Female swordtails reach 16 cm and males 14 cm including the sword, about twice the length of a 7 to 8 cm molly. In confined spaces male swordtails form dominance hierarchies and spend much of their time defending their rank, and male mollies court the females persistently. Neither habit helps in a crowded tank.

Start with a tank at least 120 by 30 cm, about 108 litres, the swordtail's minimum, with planted areas and open swimming space. Keep more females than males in both species, and watch the first weeks: if one fish is chased constantly, move it.