knifefish

I have found 2 potential sellers of p. congoensis in The Netherlands where I live, but I am afraid that they might confuse a p. afer with this one. How to definitifely distinguish the one from the other? All pics I found are inconclusive and I have never found a list of unique physical features...

It was sold to me under the wrong name, and unfortunately can not find anything but the more black colored Elephant nose Kinifefish. This guy has more brown mottling. I will try to get a better pic. They are going for about $35 at a local shop in Southern California. Thanks, Shane.