My hongsloi is very interactive. He comes over to look for food when he's hungry and will eat from a pipette. He's also very sure of himself, not shy at all. Just need to get him a girlfriend now. lol.
not apistogramma but nanacara are generally small under 3"
My house mate just got some nanacara taenia and they are awesome monty (tri-mar owner and dwarf cichlid aficionado) said absolute max if your really luck 2 3/4 inchs for male and 2 1/4 inchs for female but he said the likely hood of them reaching that size is very rare.
They're not technically apistos, but my Apistogrammoides pucallpaensis are tiny, with the male maxing out at about 3.5cm The one in my signature (first pic) is of my little female, and my male is absolutely stunning too with gorgeous gold colourations with silver spots ^^