Loaches Online Forum

Just bought 2 loaches for a 10 gallon tank about 3 weeks ago, already had 5 gold barbs & 2 Odessa barbs in tank. 1 loach large, the other, quite small. The small one was initially very active, always swimming, digging, hardly ever hid out. Didn't look very colorful at first, but now good color. They both ate well. Last few days, the small one lies in the gravel, only moves when the other loach nudges him (will swim off, then lie in the gravel again). Doesn't seem interested in food. The other loach seems OK, but has always hid more. Swims around and eats better now though. Should we be concerned about small loach? No signs as yet of sickness. All other fish very active and healthy looking. Feed flakes, frozen brine shrimp and wafers. Change water 2X week.

most of the guys here will tell you a 10G is way too small for loaches...
They won't behave as expected in a crowded conditions.
Find your loach here
http://www.loaches.com/species-index
for more info.

What loach species is it? If you go to the species index you can find all kinds of useful species-specific information. Given your description I would be very concerned, but you definitely need to educate yourself about these wonderful fish!