Here may be the answer. If you turn on the siphon in summer after the lake has formed a thermocline then the deep water will most likely smell. If you do it in winter spring and late fall after turnover (or when lots of rain) then the deep water has O2 and less sulfur smell.
Eric,
Why would he want to siphon off the water when it is no longer anoxic? What am I missing here? Or did you mean turn on the compressor at those times?
Sorry not something I'm used to dealing with as I use diffusers to break up the water columns in my ponds. And my ponds are not very deep.
