Is it harmful to put plum after fish has been put in fish for a few days?

Harmful, Yulebao and nitrifying bacteria cannot be used at the same time.

Nitrifying bacteria belong to beneficial bacteria, whose function is to convert ammonia nitrogen in water into nitrate, so as to avoid poisoning fish, while Yulebao has bactericidal effect, so it will cause harm to nitrifying bacteria. Usually, the function of Yulebao is to treat water and eliminate chlorine and other harmful components in water. Personal fish farming is generally not needed, and trapped water can be dried.