Let me state I have pretty healthy pond about 8' deep, other end between 2'&4'It has had no problem with fish die off until the drop in water levels.My thoughts are and they may be off base but lack of oxygen has caused the die off My neighbor said he drills a hole once a week with his ice auger and improved his situation.I believe alittle effort would go along way.I already have a 5000 watt generator which is why my thoughts turned that way (along with ethenol junk gas and running it would be a good thing).I havent had an issue during the summer although Im sure year round wouldnt hurt.
Keep the info coming as I stated I know zero about this