Algaecide Overdosing in a Pond

I have a pond of 3.5 m2 with Koi fish and a problem with algae so I would like to calculate the correct algecide dose for my pond.

How is the amount of algaecides calculated for a lake or a pond? Is there a formula?

Which factors, in addition to the amount of nutrients and lake size, affect the formula most?

What are the consequences of overdosing a pond or a lake with algaecide and what will happen to aquatic life? For how long will the effects of overdosing be noticeable?

What can be done to reduce the negative effects of overdosing a smaller pond with fish?