Black kuhli loach
I got in Black kuhli loaches (Pangio oblonga) this week, and they are squirmy and adorable as all little loaches are! Great in groups with small, peaceful fish- they make an active and exciting addition to a tank.
This video shows their behavior when in HUGE numbers. They prefer a sand substrate, which they will actively burrow into, coming out en masse at feeding time to swarm live or frozen foods, though they readily accept dried pellets or other sinking foods.