Found this on the internet for you. Don't think its your fault think theres a problem with the breed:
Sick Kuhli Loaches
Thank you for considering my question. I actually have two which are related.
1) My local pet store used to be able to get healthy Kuhli Loaches all the time. In recent years (no matter the source) they arrive sick and the whole lot of them die. The symptoms are reddish gill area, then swirling, then they die. Any recommendations. We would love to be able to get some "new stock" in our area.
2) This is my main question, the first is background for what knowledge I do have. This morning I discovered one of my Kuhli Loaches is pinkish around the gill area. I have had my Kuhlis for quite a long time and have not introduced any new fish for - 6 weeks. What is my best bet for treatment? I don't want him to follow the same fate as those at our pet store.
<<Hello. Kuhli loaches are a problem lately in most stores. The stock is just not healthy anymore, and they seem particularly prone to bacterial infections and gill flukes. Stores can treat them with antibiotics, and if lucky, some may survive. Strong antibiotics will kill your nitrifying bacteria, though, so be careful! For you, I would recommend Melafix and salt (a teaspoon per gallon). Or you can try to find yourself some Maracyn Two, which is a safer antibiotic to use since it's relatively gentle, and not as much of a threat to your nitrifying bacteria when used as directed.
To prevent further Kuhli problems in your tank, maintain good water quality and do regular gravel cleaning. This will help keep the nasty bacteria levels in your substrate under control, which promote infections, and prevent anoxic areas from developing underneath your decorations and rocks. It's hard to vacuum using a regular siphon, since cutting your Kuhlis in half with the tube is always a possibility, so what I recommend is that move the decorations around, and you "sift" the gravel with your hands regularly to release the debris, and let your filter remove it. Make sure you have good water circulation, so the suspended debris is removed by your filter. If need be, you can add a powerhead to your tank for circulating the dirty water during this cleaning process. Then clean your filter floss and do a water change about an hour later.
Also, if you happen to see the solid black Kuhli loaches for sale, buy them instead. They are (thus far) much hardier, easier to keep, and just as entertaining. -Gwen>>
Hopefully some of yours will survive and be super hardy thats what happened with mine, the two I have left and really fat and hardy!!