I never got one on pellets,I have owned three.People do seem to be able to do it without an incredible amount of difficulty I just couldn't do it.
One of mine was on pellets when I purchased it but there were some other fish in the tank that only ate market shrimp so I had to feed market shrimp,and as a result the aro was accidentally weened of the pellets and krill and never accepted them again after that.
I purchased mine from kory at UTA back in april,he was maybe 4",I just sold him in the first week of January and he was about 11"......thats with a diet of almost only market shrimp,maybe sometimes a nightcrawler but thats it.