There are laws against practicing veterinary medicine without a license that may be enforced on occasion*. What is the Practice of Veterinary Medicine?
In this document I discuss the different pitfalls of helping people with their sick fish. Sometimes people will ask you to help them with their Koi and pond fish and you need to know where it gets “sticky”.
If you render a diagnosis or prescribe a treatment for someone’s animal (not your own) without a Veterinary License, you can get in trouble.
https://drjohnson.com/wp-content/uploads/2019/10/Veterinary_Practice_Statement.pdf