Depends on the species but they do grow about like the normal colored ones do. The bristlenoses are small but the sailfin plecos can get big like the marbled ones do. I have seen two of them lately that were true monsters of over a foot so I finally broke down and bought two smal ones. They are expensive compared the the regular colored ones. I got mine for $ 25 each but have seen the little ones for as much as $ 40. Just a fish I had to have.
Jack