Well for one thing folks might not realize what your talking about from the title... they go by many common names. Some people dont even know they are a loach, often sold as a pleco. There is the occasional person on here that has em in a regular community tank though, but if I am going to do it I am going to try to setup a specialized tank for them. Thats the next project after my 240g is complete. They arent very common in fish stores around here, think I have only seen em in one. But there is a local guy selling some that he breeds, if anyone is interested check out
http://brianstropicals.com/ohio_tropical_fish.html he has Sewellia lineolata. If you want to talk to alot of folks that have em though, check out the forums at loaches.com, there are many that keep river tanks.