Methods to identify when a guppy is about to lay a small fish:

1. The anal fin is square. Before guppies give birth, their belly will become larger and wider, and their anal fins will also undergo great changes. The anal fin is round before pregnancy, becomes square after pregnancy, and becomes a rounder square before delivery.

2. The fetal spots are obvious. The anus of guppies will protrude before giving birth, and the fetal spots around the anus will turn dark or black.

3. Behaving irritably. Before giving birth, guppies will be irritable, will stay in one place, and will drive other fish away.

4. Decreased appetite. When she is about to give birth to baby fish, the female fish's appetite will be severely reduced, and she often will not respond when feeding.

5. Black excrement. When a guppy excretes black urine, it means that the guppy is about to give birth.