1. For a long time, all Auchenoglanis (they are not the only genus that are called giraffe catfish) were pretty much all thought to be A. occidentalis.
Go figure now! We must wait until the ichthyologists come to some kind of agreement. FWIW, yours looks much alike to about half a dozen I ever had and I thought they all were Auchenoglanis occidentalis http://www.planetcatfish.com/common/species.php?species_id=149
Looks like this to me. If it is, it does not look like a good specimen however (health looks poor). They need some shelter and they generally spend a large amount of time foraging in the substrate. A tank with no substrate and no cover is going to be stressful. Diet is likely mollusks, invertebrates, plants, snails, etc.
And for the sake of discussion, I find it difficult to believe that this can be only 2 species covering an area that is the size of America x 2, occupying completely separate lake and river ecosystems.
I don't know what he is, but he looks better in the 2nd picture. Did you get him some hiding spots? They need them. Also they want sand to sift through for food.
there are hiding spots, but i dont like using sands or gravels in my tank. All my cats are in bare bottom tank, and they're doing fine and eating like pigs.
Having kept at least 3 species of auchenoglanis, your's greatly resembles an auchenoglanis wittei such as one I raised to 19" and sold months ago. I agree that in the first photo's the fish does appear stressed but looks better in the later photo. I've found that they do like dim light, large shaded hiding spaces and a gravel substrate as they do seem to enjoy sifting through gravel searching for food and as a result if using gravel, that will keep it very clean and free from sedimentation. Here's 3 photo's of my former a. wittei for comparison, one as a stressed juvenile the first day home, one at mid-growth and one as an adult at around 15"...