Can Guppy Live With Green swordtail?

The water could hardly match better: swordtails take 16 to 28 °C and guppies 17 to 28 °C, and both want pH 7 to 8. The differences are size and space.

A female swordtail reaches 16 cm and a male 14 cm including the sword, around three times the length of a guppy. Swordtails are generally peaceful and mix well with similarly sized community fish, but a guppy is not similarly sized, and swordtails are among the livebearers that can show aggression, unlike the placid platy. In confined spaces the males also form dominance hierarchies and spend much of their time holding their positions.

That makes tank size the deciding factor. A small group of swordtails needs a base of at least 120 by 30 cm, about 108 litres, far more than guppies need. In a tank that size, with planted areas and open swimming space, the guppies have room to keep out of the way. In a small guppy tank, leave the swordtails out.