Good call.
This one looks like a good example of that: I had an alb. sen. grow from about 3 1/2 inches to 8 1/2 inches in like 7 months 'til he got spooked out of the tank during a lightning storm.
With out a doubt my pleco i bought him at about 4 1/2 inches and that was about 3 years ago i have feed him algae pellets,carrots,cucumbers plenty of times and the little guy refuses to grow he is now a whapping 5 inches...so my experiance 1/2 inch in 3 years with a darn good food supply yep thats about as slow as it can get i grow faster than him and im fully grown lol