Onefish2fish, makes a good point. If fish are to be kept long term,, they will eventually need a large tank 100 gal would be minimum in my view. It is said that clowwn loaches grow rather quickly from juveniles to five inches long and then, growth slows somewhat. Given their sensitivity to less than ideal water conditions few ever reach the twelve inches that 2fish rightly pointed out.
My own observations thus far,indicate that they do better with current and high oxygen levels. Frequent small water changes are perhaps needed as well.