has an article on breeding clowns. I don't really believe the article though because there are no follow up articles and the same process hasn't been reported with repeated success.
To be brief, clown loaches will only breed when they 10+ years old and over 10 inches long. I'm not sure if Clowns can be sexed before they are full grown. They can only be found in West Kalimantan and Sumatra and start spawing during the raining season. The water that they spawn in probably gets very acidic from the flooding of the peat forests.