i had ich once and did a salt treatment in my 75 and i noticed no difference in the plants, and it was gone in about a week and a half.
i wasn't trying to be insulting to you, though i see how it came across that way, and i apologize for that. i realize that the water 'requirements' for your catfish are somewhat misunderstood, or even controversial if we want to go that far. maybe you and your guy have the 'magic touch' for keeping them healthy in freshwater, but most of the problems i've seen are nasty skin conditions/infections related to being kept in freshwater. this is why i tried to back up my thoughts with a couple "expert" sources rather than just being like "i heard about this one time. . . . "
really, the whole reason i brought it up was because it seems like you really care about your plants, so it seemed incongruous to mix the catfish in there based on what *I* consider their needs to be. So i figured you didn't know. I didn't mean it as an attack.
There are many fish that need/should have brackish water - dragon and other gobies, most types of eels, most puffers, even some types of cichlids and rainbowfish. Whether the store tells you about it, or just sells you the fish to make a sale is hard to predict until you go there. I've been to some places that keep their mollies in brackish, other stores I'm sure wouldn't know brackish water if i slipped it into their water bottles, and they're selling some very 'aggressive' dragon gobies which will 'eat anything that fits in their mouths'.
You are going to do what you want to do, whether that's doing more research (which is the goal of all of us here), keeping the fish as-is, or finding them new homes. All i can do as an anonymous internet persona is try to educate. I can't come over there and make you (or anyone else) do what I think is right, and i sure as heck don't want no brackish fish. i barely salt my food, i don't think i could salt my water too.
As a matter of fact, one of them has developed a protrusion extending from one of his gills (just today, it wasn't there this morning =/...). They're pinkish white (mostly white), and perhaps half a mm long. There seems to be three but very bunched together. It almost looks as if something got stuck in there rather than something extending from the gills, but I'm sure that's not the case.