It depends on the species. Most of the albino polys that are available for just a few bucks hit around 9-10" as Anne says. I have a couple out of 15 that have reached the 1ft mark. There are also albino variants of ornates that grow to more than 20". And, I know of an albino endli that has passed 28". Neither of these 2 are old so, there may still be some additional growth ahead of them.