I just measured my clown loach. I have a steel knife inside the tank to keep a cucumber down. The clown loach from nose to tail is the lenght of that knife roughly, if not a very tiny bit longer. The knife is 9 iches
That fish has grown faster than any of the clown loaches in the tank. Although one of my 4 year olds is quite large and probably over 7 inch based on the size difference with the large clown. So some look stunted some grow like weeds....Perhaps its do do with their sex and most of the others are males...?
I've had this loach for 3 years now...It means he/she has grown roughly an inch per year since I got him. For an older clown loach that sounds quite a lot. He definately gets most of the food though