Cinder, i'd also like to point out that there's not only ONE species of hillstream loach. Hillstream loach is just a basic name given to a sub-family of loaches with many many members. Beaufortia kweichowensis is usually one of the most basic types seen in local lfs's. Multiple types of hillstream loaches look exactly alike, with only a little variation here and there in stripes and coloration, others look more like a shinese algae eater with large pectoral fins.
They are a great "poorman's stingray", very different from a stingray but one of the closest things you can get to it without having a tank around 180 gallons.
Don't trust any local lfs with your stingray unless you are sure they know what they're doing. Many couldn't even tell what type it is, or have it stuck on ghost shrimp or blackworms. Black worms and ghost shrimp are the most commonly accepted food items by smaller stingrays; sadly if fed constantly they'll ignore any other food you put in with them.
The biggest thing that annoys me is they don't know what type it is. Usually they just plaster a sticker on the tank saying " Teacup Stingray", sorry but that's a name used for ANY stingray in the 4 inch diameter area. The only stingray that's usually dubbed this name when NOT around 4 inches is Potomatrygon Reticulatus. It's usually best you look up the types after reading basic skills and get acquainted to each species and what it looks like if your buying from your lfs. Many types look slightly different when smaller and some will even look the same as another species.
Keeping them with tankmates is a tricky business, sometimes the fish will pick at the ray's disc or tail, sometimes the stingray will try to eat the fish. Personally i've kept mine with needlenose fish, jaguar cichlids, and larger bichirs for short periods of time with nothing bad coming out of it. It would of course probably be a different story if the stingray was fully grown.
My three basic tips for success in these:
1. Like said, have a very stable environment.
2. Have the biggest tank possible, starting at about 150 gallons for a full grown ( larger for flower rays, etc. ).
3. Order it offline from a REPUTABLE dealer. Don't go onto aquabid and bid on some 100 dollar stingray from some guy that's never on. There are plenty of forums and sites that have dealers that specialize in only stingrays or large tankbusters in general. Search for monster fish, predatory fish, etc.