Pond Boss Forums POND CONSTRUCTION Building a dam How deep is too deep?

I know with lakes and reservoirs there is a level at which below it there is little oxygen and I wanted to know if this applies to ponds that are built very deep such as 20-40ft. I would think that a strong enough (capacity for water volumn)
pump system would alleviate this problem all together but is there a depth the becomes counter productive to most pond owners goals.