The majority of people that ...

 The majority of people that are providing answers are either trying to sell you something or are providing partial answers to a very complicated problem. The odors could be related to anaerobic activity, but it could be the odor issues are also related to the type of algae that you is growing in the pond. The first thing to consider is controlling the algae growth in the pond. Facultative ponds require algae, so you don't want to eliminate all the algae. But you do want to control it.  You can do that using algicide products such is liquid or a granular copper sulfate.  You could also partially cover the pond to control the excess of algae growth as was recommended in another post. If the problem is related to aerobic activity, once again in facultative Ponds you do not want to eliminate the  anaerobic activity. You just want to control it. You can use chemicals such as chlorine or Chlorine dioxide or calcium nitrate.  Chlorine dioxide combined with algae will often produce an odor very similar to cat piss, so be sure you to proceed with caution. You can use bacteria products as well. I Recommend evaluating all the options and look at the cost.