6"? Lol! I've seen pass 10" and almost 11". Your probably seen a stunted one or not eating enough. Records is planetcatfish is not really accurate as their are more than one time of Galaxy vampire pleco.
I traded my female L240 at 8.5" and still growing (pics in my albums). These are REALLY slow growing after the 5" mark. Stunning fish and one of my favorite plecos.
Here is the video
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