There should have been a good water change and a cleaning of the mulm from the pond bottom before medicating. Sea salt and water conditioner salt which has no additives can be used. To medicate the amount would be 2#-3# /100 gallons of pond water until you see improvement. The salt must be dissolved before adding. It might be best to issolate the sick fish to a small tank to treat. The frogs will move out if they don't like the salt. Good luck.

I honestly do not remember the differences, and it has to do with the trace elements and the process in which the batches are made. I trust synthetic sea salt over using "Pond" salt. You can use Kosher salt because it has no iodine. Pick up a large bag of Sea Salt for the best buy. Do not just dump in a pound. Add say a 1/8 cup every day that has been diluted into say a milk jug of water, slowly into the skimmer. Adding it via a syphon is much better. You can see the light bending as the salt water mixes with the fresh water. At that point your fish are getting a head rush and adjusting to the new equilibrium. Many alga will not tolerate salt and will diminish over time.

If the bottom is not covered with rocks, other maintenance is adequate and you are testing the water I would guess you have something organic like a raccoon or squirrel, or even a bird dead in the pond. After only a month that seems the most likely problem. By this time feathers, hair and fatty particles would be showing up in the filters. If you find such a thing in the pond, the water and filters will still stink until bacterial balance shifts from anaerobic to aerobic. Water changes and clean filters will make the process faster. Scoop and vacuum all debris. Check under the plants. They could hide the problem. All the additives are for special circumstances. Do you really need them?

Toad tadpoles don't taste good to fish so if you had some X-rated toad fun in your pond there should be some tadpoles. Do you have a turtle? They'll eat them. I'm in MI, too and I have very few tadpoles this year. Usually I have tons of tree frogs (one year there were almost 100 of them) and toads trilling but not this year. I have heard 3 male tree frogs and 2 male toads (they have given up and gone home now) but have yet to see any girls. No girls, no tadpoles. I have a few big green frog tadpoles in the stream and a few smaller ones we haven't identified yet but that's it. There are always a dozen green frogs in my pond but this is the first time I found the tadpoles in the stream. Mama frog was smart. Only toad tadpoles will survive in the big pond with the fish. Some S@B dug a huge shallow hole down the road from me, that was full of water all winter. He has been slowly filling it in over the last 3 months. I wonder if they went there instead? I'm not sure I want to go check because if they are there I'll feel the need to do something about it and I'm already disappointed with the DNR over a turtle incident from last week.