Question

What do you think if all the fish in a pond die? How will it affect the pond ecosystem?

Answer 1

it will affect the ecosystem of pond as
the pond will not be clean as before

Answer 2

A lack of dissolved oxygen is the most common cause of fish kills in ponds. This occurs frequently when aquatic plants and algae die in the summer or when they are treated with aquatic herbicides. Fish kills due to low oxygen are most common during hot, dry spells when algae grow and then die quickly.