With the exception of the stingray pleco (not a real pleco), I only use the term pleco of it has the typical "pleco" features...body armour, large mouth for clinging to the glass, dorsal & pectoral spikes. Farlowella, chinese algae eaters & such I wouldnt call a pleco.
exasperatus2002 wrote:body armour, large mouth for clinging to the glass, dorsal & pectoral spikes
Parotocinclus aripuanensis has all these things There aren't really any rules as such for calling something a pleco, I think in this post it has been taken as shorthand for saying loricariidae.
For what it's worth... I've seen a ?Nannoptopoma and what looked like a minute Otocinclus for sale which I'd say were about 20 mm TL. I didn't recognize the species, but they looked adult to me, so it is possible there are more species of about the same size as P. aripuanensis.