To be specific... More Panda Cories, your lone Panda is a Sad Panda... LOL.
They are MUCH happier in shoals of at least 6 fish, and the more the merrier.
In the wild they roam in shoals numbering from hundreds to thousands, yes thousands of fish in one school.
Several species of cat/pleco stay rather small, <4".
Common in the trade are Clown Pleco, Rubberlip/Bulldog Pleco, South American Bumblebee cat (a favorite of mine), Banjo cats and more.