Don't assume that all the fish are dead. Do all you can to determine that for sure. Look for feeding splashes, fish with rod-n-reel, set traps, use limb lines, maybe even buy some feed and try feeding the pond for a few weeks...ect. With the dead fish count you described, I would think that there are many fish left in the pond, but dead fish do not always float so, who knows.

Common opinion here at PB is to start the air up and attend the initial 15 minute run and smell for the sulfur/rotten egg smell...stop the air if you smell it. Continue the next day with the same approach. Once you get to a good 15 minute run, double it the next day (30 minutes) and so on until you are running the desired amount of time per day.

If you have truly killed off the pond, I guess you could just turn the air on and let it run. Let's see what other say about this before taking my advise on this.

With your single diffuser, pond size, and location, I would think that you should shoot for 24/7 air time throughout the spring, summer, and fall months. We'll have to see what other northerners do for their wintertime aeration.

Using the sprinkler head should not hurt anything, but I have to ask where the water source is coming from. Well water rarely has any DO in it to begin with, but the time it spends in the open air and the surface disturbance that it causes should help.

Restocking the pond would be fine to do anytime after you get the aeration up and running or turn it off for a week or so. I'd determine what has survived and get the air up and going before making any stocking decisions.

Welcome to the forums, glad you found us!

Fish on!,
Noel