The stuff I used from the aquarium store is called NeoPlex Marine and Freshwater Medication. It's a neomycine sulfate product. Powder form. It's labeled for addition to aquarium water - no mention of oral application, but under the circumstances I didn't see a downside to trying it.
I just mixed in an amount that "looked right" with a couple tablespoons of Optimal and some minced bluegill/crawler meat. Nothing scientific about how I did it, but it worked. It seems they don't particularly care for the taste of the medicine - if I put too much in the feed they would spit a lot of it - so I had to fiddle with the amount for the first couple days. After they got used to it I've increased the dose and they don't seem to be terribly put off by that.
I went from losing one or two a day and the rest of them with fin fungus to apparently healthy fish within a week. I can still see a bit of fungus on two of them, but it's less every day. They are eating like pigs and getting fat. I try to feed at least three times per day, and I drop it in until they stop taking it. They all look like tiny little footballs now.
This is a very small sample, but it has led me to decide that any new fish that come to my pond will 1) be caged for feed training, 2) receive medicated feed for two weeks post-arrival, 3) spend a few minutes in a tank of salted (Snipe walleye handling tip) AND medicated water before going into the cage in the pond, 4) when I travel to buy fish in the future they will come home in medicated water.
Aquarium store guy gave me a tip that I think will come in handy for training/medicating fish that tend to be bottom feeders - take whatever fish/bug/worm/pellet/medicine mix you're going use, spread in a very thin layer on a teflon cookie sheet, pour plain boiled gelatin over the top just enough to bond the food mix, refrigerate until cool. Then peel the congealed mixture from the pan, chop/shred to appropriate size, and feed it out. They will eat some of it on the drop, and the gelatin will keep what makes it to the bottom in coherent bits they can find and eat off the floor.
He said to guesstimate the amount that will be used in a week and make that much in one batch. Keep the mixture refrigerated. Only take out the amount required for a single feeding. When you run out just make another batch.
I plan to try this method for starting my YP when they come.
