just to toss my 2 cents in... i about 5 weeks ago i picked up two Albino BNP (Bristle Nose Pleco) and i see them ALL the time scooting along the bottom and up and down the glass. i've heard on this forum and also read that for some strange reason the Albino BNP are extremely active at almost all hours day or night and in my experience its very true.
they are adorable and they max out at around 6-7" (I believe) but someone else my be better suited to give a max size.
Edit - From LiveAquaria.com:
http://www.liveaquaria.com/product/prod_display.cfm?c=830+837+1039&pcatid=1039
it says "Bushy Nose" but i'm almost 100% positive they are they same fish, site also says max size is 4 1/2"