Ooh, thank you for the dishwasher tip! I like that. But honestly, I'm considering just trashing the tank and everything in it. It's just a $9.99 1-gal, undergravel filter pastic tank from WalMart. Just not worth all the aggravation (or potentially more sick/dead fish!)
The little guy is doing no better today.
He now has a small red spot on his side, and some red streaking in his fins. Septicemia now? Poor dude! He will get his second dose of tetracycline shortly.
Thank you all for the wonderful input and encouragement, especially MoonShadow, who has been holding my hand via facebook since yesterday. You're the best, girlie!