Given ample and varied meaty foods, clown loaches grow moderately fast. I've had them reach close to max size in 2-3 years.The question I am wondering about is.... How long does it take for them to reach about 5 inches? I know a guy that has 2 that are around 7-9 inches and he has had them around 7 years, he keeps them in the 265 gal display in his fish store in Pa. So if it would take 2-4 years to reach that size then that would give ample time to plan for a larger tank. Just a thought. I agree with the Khuli's, I think that would be a better choice and they would do great with sand and plants.
If this is the case, they are severely stunted. (I know a guy that has 2 that are around 7-9 inches and he has had them around 7 years