I was going to post my sugestion last time but your fish were already past the help line, in my book. This is very risky for someone that hasn't done it before, but will kill most everything in your pond, and your fish if your not careful.
Here goes.
Loose the salt, good for Margarita's that's about it.
Know exactly how much water you have in your pond, exactly.
Get some Potassium Permanganate.
If your on well water do a heavy water change 50% or more,
IF, you have a lot of suspended debris.
Bypass your filter, but keep the water moving and have good airation.
Have a few bottles of Hydrogen Peroxide on hand, this revereses the effects of PP. 1 cup, to 1000gal.
Do a 3ppm dose of Potassium, the first day it won't last more than a hour or two, but right as the PP is changing color you should be able to net a fish, gently, and pull it up to the surface, and everywhere there is a brown spot, is dead bugs.
While the PP is in the pond pay very close attention to the fish's breathing, if it gets to labored (on the first day it shouldn't) dump in some peroxide, but only in a emergency, as you won't be able to dose again the second day with the peroxide in the water.
Second day dose again PP at 3ppm, today they will probably start having a hard time breathing about 2 hours into the treatment, but try to let them go in it for as long as they can.
Do not leave the pond unattended for more than a bathroom break, keep watch on them as best you can.
You can find more info on how to measure PP to get the ppm rate you need here:
http://www.click2roark.com/cgi-win/w...ocument=index2 you will have to log in to access the info.
This is a very risky process, if you are not comfortable, don't do it. Do as much reading by doing a google search on PP before hand. Many people are very scared of PP as they have killed their fish with it, but it can be one of the most effective means of clearing parasites I have ever used, and when the process is done, and you pull a fish up to the surface, you can physically see what was killed by means of browns areas all over your fish. PP is not a medication, it is a oxidizer, so it will not heal your fish, it will just kill the bugs. This is my recommendation, but mine only, don't hold me liable, if you don't understand how to use it, don't use it. Being I can't see you fish, they may or may not be able to handle the stress of PP, but if you want to save them, and understand there is a risk involved of losing all of them, I'd take the risk, and use it. As you saw what happened last time, and you lost them all anyways..