Posted: 30/11/2013 at 15:05
A pond will only become foul smelling because plant or animal material is decomposing in it. Adding a pump at this stage will probably not solve the problem.
I would be inclined to drain it completely, give it a thorough clean and start again. A well balanced pond shouldn't need any additional aeration, but the reality is that most of us over stock the pond with fish, I know I did, so some assistance may be needed in hot weather.