And just to confuse you further, they are much better in larger groups than four. The minimum is said to be 3, but they can be very shy. If you have more of them, they tend to show themselves more, and thus are more enjoyable to have.
I had a black kuhli loach manage to jump from a 25G tank, on its shelf in front of the window, to a 5G I had on a short stand, three feet lower down and three feet away. How it managed to be lucky enough to land in the 5G and not the floor, I don't know. I didn't even know he was in there for who knows how long because, being alone, he hid all the time. Found him while rescaping the plants. They sometimes get going quite fast and can be jumpers. A cover is a good idea.
If it were me, I'd choose another fish for a 10 G, or get a larger tank so you can keep a decent size group of the kuhlis. They need lots of hiding spots, and will try to wiggle through the smallest space, so no rough rocks that could really scrape them up. Lots of plants, wood, smooth rocks, for hiding spots. I had three of the striped ones who spent their days twined among the floating stems I had rooting while they floated, in a thickly planted tank. I used to wonder if they were sick, but they were just, forgive the term, hanging out.
Personally I think a 29G is better, and you could easily keep 10 or so, with some other small fish species for the mid or top levels. Strictly my opinion.
