well it may be just a juvie peppermint then, but they usually are solid black. the only other one that springs to mind is the L004/005/028/073 Angelicus Pleco Hypancistrus sp. They have that light stripes to, and have varied numbers of spots (all of the same small size) and the lightness in stripes change too. the spots are said to get smaller with age, and they may become as light as the one below, check out http://www.planetcatfish.com/catelog/loricari/hypancis/10_F.PHP. the other one is a similar match to yours. i'll have a proper look tomorrow, im nackered now