Clown Loach illness

Question
Chris,
I have a fish health question, specifically about a clown loach (3") that has recently acquired white "sores" on the dorsal part of its body and caudal peduncle. Before I go any further into the specifics of my questions, I have a 90 gallon tropical community tank that has been set up for ~3 weeks after being moved a short distance from it's original location. The community is dominated by 4 silver dollars, 2 bala sharks, 2 clown loaches, and a few smaller tetras and catfish. I certainly don't think that it's overstocked and have been doing ~1/3 water changes every 4 days or so since it was moved (recognizing that biological filtration would need time to get going). Here's the water chemistry as of earlier today (prior to water change): NH3 0.25, NO2 .25, kH 2, pH 6.9. All fish other than the single clown loach have been fine and show no signs of stress, but this particular fish has not seemed to have equilibrated after the move. It's behavior has been generally listless and inactive (and becoming more so with time), although it frequently and aggressively scrapes the dorsal and caudal parts of its body on decorative rocks in the aquarium. The "sores" correspond to the parts of the body that come into contact with the rocks, but I can't say whether the "sores" came before the scraping, or vice versa. The "sores" are whitish patches that are a couple of square millimeters in size. They don't appear to have any strands of mucus or fungus, but the behavior of the fish suggest that they are causing some sort of distress. I'm sure it's difficult to diagnose fish disease like this, but can you suggest a few likely culprits that might cause these symptoms and behaviors? Thanks for any information.

Brandon  

Answer
Hi Brandon;

For whatever reason, this particular fish could be more sensitive to the toxins that rose while the tank went through a "mini break-in". Or, he injured himself and is now more irritated from scratching and it has become infected. It might be a good idea to separate him to a hospital tank with fresh clean water. Make it a bare tank with no gravel or decorations. Just a heater, airstone and lights. 5 or 10 gallons is plenty big for a little 3 inch clown loach. You might want to treat him with Fungus Cure. He has probably developed an infection that got into the skin from scratching. This would explain the lethargy as well.
Change 50% of the water every day, right before that day's dose of medicine. Hospital tanks often don't have a biologically functioning filter so the water changes are essential.

If the lesions are on the back of the fish like a saddle, it could be columnaris. Columnaris looks like fungus but is a bacterial infection. Here is an article about it;

http://freshaquarium.about.com/cs/disease/p/columnaris.htm

I hope he feels better soon.....

At Your Service;
Chris Robbins