How deep can a pond be to avoid anaerobic decomposition?

Question

it's a pond with organic matter with not much water movement

Answer 1

Thats the problem....you need water movement so that there is a constant flow of oxygen into the water.  Dissolved oxygen is very important and can effect the entire ecosystem.  You would need soemthing like an aerator that could bring oxygen in.  A practical idea would be to install a fountain or something that would keep the water churning.  Even then it is going to be difficult to avoid if it is a large pond.