Extraordinary claims require extraordinary evidence, which with all due respect ya haven't provided. Seen too much over the years to outright say bull crap, but I don't see a 12" fish in the pics provided, or even an 8" fish. I see a nice-lookin' male BN which I'll estimate at app. 5", plus or minus a bit.
Just saved the pic and will be pulling out photo shop a bit later tonight, after I'm done with feedin' my own finny friends. If that's 1/2" glass, then by measurin' the thickness of the glass and then rotatin' it, there's a built in ruler in the photo. All I hafta do is figure how many lengths of glass thickness that pleco is and divide by 2 to get a length in inches; a quick rough judgement by eyeballin' it is that the fish has a TL of 9 or 10 "thicknesses" of the glass, which puts it at 4 1/2" to 5".
WYite