I am certainly not expert when it comes to Apistogramma species, but I would suggest A. agassizii and A. gephyra as possibles. Once he settles and you can get a more representative photo, the patterning in the caudal fin should be distinctive as it is between these two species which both have a lanceolate caudal fin.
Now, within the "species" A. agassizii I understand there are eight recognized forms which may turn out to be distinct species (Mark Wise). See Miller & Schliewen, "The molecular phylogeny of the genus Apistogramma," DATZ 2005, and Koslowski (2002). I only have these references, not the studies alas.