Problem wth dwarf loach?

[ey]

Last week, I moved 8 of my Dwarf loaches (about 3cm each) from my 29g to 95g tank.

They settled in with no issues until I noticed one of them looking funny tonight. One of the dwarf's mouth has no colour on it. While the other dwarfs all have the black line/pattern extending from its tail all the way to its mouth, this one dwarf does not have any colour between its eye and its mouth. Its' barbels are not damaged in any way though and it is behaving/swimming just like all the other dwarfs so does not appear sick or infected. It's a bit hard to explain and a photo would definitely be clearer but the dwarf was moving so fast I could not get a good shot of it.

I tested the water paramters, everything was norma, i.e. 0 ammonia, 15 nitrate, 0 nitrite, pH 6.4. I have been doing 20% daily water changes since last Tuesday. The only change is I have transferred gravel from the 29g tank to the 95g tank. The gravel (small non-sharp pebbles) are the same type in both tanks, however the pH from the 29g tank is 6.8. I did soak the gravel from the 29g tank in the 95g tank water for 8 hours before putting the gravel in.

I cannot think of any possible disease this may be as all other fish in the tank appear to be acting normal. The only thing I can think of is the dwarf might have taken a few accidental knocks from the significantly larger clowns/yoyos when darting in the tank. With the limited space in the tank, this may have contributed to this problem. When they were in the 29g tank, they literally had the whole tank to themselves, whereas they are now right at the bottom of the loach pecking order.

I hope it is nothing more than a light injury that the dwarf can recover over time, otherwise is there anything I can do at the moment?

[Diana]

A clean looking spot, perhaps a shallow scoop out of the fish may well be a minor injury such as bumping into a rock, or getting scraped against the container you moved the fish in. A larger patch that does not look like a shallow hole, and does not look shiny might be the beginnings of Flavobacteria columnaris, AKA Flex, columnaris, or many other names.

Either way the first line of defense is exactly what you are doing: Plenty of water changes. This will keep the nitrate as low as possible (can you get it under 10 ppm?) Flex grows faster when the nitrate is elevated. More water changes also lower the level of bacteria and fungus spores in the water, so there are fewer to infect the fish.

Melafix and Pimafix can slow the growth of bacteria and fungus, especially on the outside of the fish. The label says they do not affect the nitrifying bacteria, but I would be cautious about using them if your tank is still cycling, even a minicycle caused by adding more fish to an established tank.