I just got a 3" clown knife fish today, he/she has four dots on each side. I wanted to know if they gain more spots when they get bigger or not. The girl at the lfs said they did...
As they mature they can change, but it can also depends on their environment. I remember someone throwing their CK in a pond for the warmer months and when he went to go retrieve it, the spots changed in just a few months. The CKs that I've kept never really changed on me, but I did have one that I put in my pond as well and it's spots turned into "flower" spots.