At any rate, I have a young clown loach who has basically suffered from all kinds of ailments ever since I got him. I'll start with his current ailment, and then list out his health history if that helps at all. To get things out of the way first, here are three photos of him that I took just now:
The loach is currently in a 10-gallon hospital tank with no other fish, but with a cycled filter. Temperature is 79F, pH 6.9, KH 40-60ppm. I'm currently treating him with Maracyn Plus (trimethoprim and sulfadimidine), partly to rule out columnaris or any other bacterial infection, and party because I'm cramming for the bar exam, and really don't have time to spare to do a labor-intensive treatment like malachite green, at least until the end of next week! So far, the Maracyn Plus hasn't seemed to do anything to get rid of the spots. However, the loach is still swimming occasionally, and I think he's eating.
And now for the boring part: how this loach got here. To make a very long story short, I bought him along with 7 other small 1 1/2" clowns from an LFS back in January. The others were in great health; this poor fellow brought ich with him. After about 18 days of using Super Ick Cure, I got rid of the ich. After another quarantine period, all the loaches looked like they were healthy, so I gave 3 of them to a friend, and moved the other 5 into my 80-gallon main tank to live with my 3-year-old, 4-inch clowns.
Things were fine for about a week. Then this particular loach started looking a little skinny and emaciated, and developed a columnaris-like whitish covering over his slime coat. Fearing skinny disease (as I've been an occasional reader of this forum), I put him in a 20-gallon hospital tank, and treated him with Maracyn-One and Two (erythromycin & minocycline). The whitish covering went away, and after some time he started fattening up as well. About two weeks later, he was good to go back into the main tank. When he went back in, the other loaches had outstripped him in growth, and were about twice his size.
After that, things were fine again until the beginning of this particular episode. About a month ago, this loach (let's call him Skinny, as that's the unofficial name I've given him) and the next-smallest loach, who had been bickering over dominance, started coming down with a whitish film again. When I looked carefully, Skinny had broad, grayish-white spots, similar to what's in the photos.
I started to suspect costia or chilodonella at this point. I attempted to treat this using Jungle Parasite Clear (praziquantel, metronidazole, acriflavine), but this had no effect. Next, I treated the whole 80-gallon tank with Rid-Ich for a week. Skinny's grayish spots disappeared, only to be replaced with ulcer-like lesions. However, I wasn't entirely sure these lesions weren't just missing skin or scales that needed time to grow back, though, so I left them alone. Last week, as the next-smallest loach was still kind of filmy, I treated with Jungle Fungus Clear (nitrofurazone & furazolidone), and removed the medication after the course had been finished.
On Sunday, I found the next-smallest loach lying on its side hyperventilating on the bottom of the tank. Skinny was hovering under the wood, and still looked infected, and, being sick and tired of treating the 80-gallon directly, I moved him into the 10-gallon hospital tank. When I went to catch the next-smallest loach, it didn't even try to avoid the net; it appeared paralyzed from below the pectoral fins. I put it in the hospital tank with Skinny, but by Monday morning it was dead.
If someone could tell me, or at least give me some insight into what the heck is going on with Skinny, and what might have happened to the other loach, I would be eternally grateful. What's interesting to note is that the other six loaches (3 large, 3 small) are completely healthy, robust, and actively doing the loachy dance in the 80-gallon. Thus, I'm pretty reluctant to put Skinny back in with them until he is in absolutely tip-top shape. And even then, I'd be almost tempted to trade him to the LFS and put off my loach school-growing activities for another time in the future. Thanks in advance for all your help!