inwards slightly, whereas the females have straight tips. The fish has a movable spine that lies in a groove below the eye, which may be extended as a defence mechanism. The spine may cause a painful wound, but is not venomous. It also may be used as a predation tool as it is set close to the mouth. Distribution and habitat Clown loaches are native to the islands of Sumatra and Borneo in Indonesia. Clear stream environments provide the optimal habitat for clown loaches, but biannual monsoon flooding forces the fish to move into flooded flood plains, or murky or blackwater rivers or lakes, for 7–8 months of the year, and clown loaches are commonly found in the flood plains of hilly areas. Breeding adults migrate to smaller waterways to spawn annually. In its native habitat, the fish is found in water with a temperature range of , a pH between 5.0 and 8.0, and water hardness between 5 and 12 dH. Reproduction in captivity Clown loach reproduce in captivity only after hormonal stimulation of final oocyte maturation and ovulation. Captive breeding and mass production of clown loach is done primarily in country of origin (Indonesia) and in Europe ( https://www.youtube.com/watch?v=qerHElt1ozQ ). In the aquarium A common and popular fish for tropical freshwater aquaria, C. macracanthus is a visually pleasing species. Although specimens in the wild will reach 40 to 50 cm, in the aquaria it is uncommon for C. macracanthus to attain more than 15 to 20 cm fork length. They are a very long-lived species, living up to 30 years. These fish have bifurcated spines under the eyes. They are thought to be used as a defence mechanism and possibly, for obtaining prey. C. macracanthus will associate with other benthic species in the aquaria if kept singly or with few other specimens. They make suitable tank-mates for any non-aggressive community fishes, but do not thrive when kept with larger, more dominant species. Occasionally C. macracanthus will exhibit erratic swimming patterns, such as swimming on their sides or upside down. This is not usually a sign of illness, however, and the fish will normally return to normal behaviour almost instantly. As C. macracanthus is found in riverine environments it is able to cope with good flow rates of water in the aquaria. Aquascapes may replicate this environment to suit the requirements of the species with areas of high flow,