From what I remember from the tri-species challenge, each Pokemon has to have a different type, not species. Unless that's what you meant.
Here's the original thread I participated in -
http://www.pokecommunity.com/showthread.php?t=234747
Also, it was called the
Trio-species. Doesn't really matter though.
I had userbars in the old thread if you want those (I need to reup them though). Again with Trio name.