I'd say paleatus ( peppered ) cory. If you have 6 then theres a good possibility you'll get a spawning trio out them. Lots of fun to watch them spawn. The female is wider than the males awhen viewed from above and shes also taller and more robust looking from the side. Have fun and good luck with them http://www.planetcatfish.com/catelog/callicht/corydora/271_1.php