Loaches

Loach is a term used to describe fish from a number of families. In New Zealand those commonly available for the aquarium trade fall into three families- Cobitidae, Balitoridae & Gyrinocheilidae.
Cobitidae also known as "True Loaches" include the popular Clown Loach, these species are gerenally busy fish which prefer to be kept in groups.
Balitoridae, the "Hillstream Loaches" are usually peaceful fish, which attach themselves to substrate using their ventral & pectoral fins, this adaptation allows them to cling on, in the fast flowing streams from which they originate.
Gyrionocheilidae, the "Algae Eaters" are hardy fish & can be popular for tepid water fish tanks, they can however become aggressive with age & occasionally with suck onto other fish, particularly a problem with large fancy goldfish.
In conclusion, Loaches can make excellent additions to a variety of fish tank setups, but is worth researching their needs thouroughly as species requirements are varied.