Medusa Pleco (Ancistrus ranunculus)

yoink

As for max size on these "Cthulhufish", there are reports of specimens up to 18" long - much bigger than 13cm.

Eric Becker

The fish pictured above is nearing 8" with his head being larger than a half-dollar. He rasps algae from the glass after lights out, but spends most of his time inside hollow driftwood, which seems to be a large part of his diet. Plant-safe unless your plants are not rooted firmly enough to withstand a whip with his tail as he swims past or burrows into the substrate. Should provide at least 55 gallons, driftwood, and large hiding places.

Oqsy