Clown loach natural environment is found in South East Asian, specifically in on Sumatra and Borneo (islands in Indonesia). They live in both standing and flowing water. For most of the year they're found in murky backwaters; however, during breeding season the adults move to smaller and cleaner rivers to spawn.
If you are a follower of biotyping the physical attributes of their natural murky waters will be very useful to you: pH 5-8, dH 5-11, temp 77-86F. The only attribute you may not want to mimic is the "murky", dirty aquariums are not very much fun to look at from my experience. Setting the tank to these conditions is important in clown loach care and can even go a long way in prevent clown loach disease.
They live on the riverbed (bottom feeders) in very large numbers. Over 20 million clown loaches are exported from Indonesia every year to be sold in other countries. The vast majority of those eventually find their way into aquariums. There is a demand for farmed clownloaches, but the facts surrounding clown loach breeding remain elusive. There have been claims of hormone-induced breeding of clown loaches, but none have as yet been satisfactorily confirmed. Some areas of Indonesia are beginning to report a decline in numbers of the clown loach, there is even a ban on the export of clown loaches over 15cm (the spawning adults). While, the impact of declining numbers has not been very large yet, there are many families counting on the clown loach exports as their sole income.
As luck would have it, the clown loach fish harvesting industry has not yet met with the industrial revolution. What I mean by that is, the process of catching the clown is very non-invasive and sustainable so it doesn't destroy the clown loaches environment. A hollowed-out piece of bamboo (about 2m long) is placed in the water near the shore. The clown loaches then go into the bamboo to hide. Then the bamboo can be lifted out of the water and with a careful shake of the bamboo the fish slide out. The single piece of bamboo can be reused over and over. There are variations on the theme of clown loach catching, but they all work on same principle. Fish that are caught for subsequent aquarium use are usually around 2-8cm in length. The hollowed-out bamboo is not large enough in diameter for the larger clowns to hide in. Larger clown fish are caught using other methods and they are normally eaten by the locals, rather than exported for sale.
Peak clown loach catching season is just after the rainy season in the South East Asian, which is from Dec-Feb. The harvesting season is from the end of March until July. This seasonal catching led to dwindling supplies of clown loaches in stores once October and November came around. Now, large clown loach holding tanks have been built in the big cities to hold enough clown loaches to keep the stores stocked year-round. The benefit for big business is that the clowns grow while in the holding tank and the bigger the clown loach is, the more expensive it is.