wes the dark phase one I have had in an 86*f tank now for 3 yrs and is a beast..very active and a hard feeder(havent seen one ill effect of the temp) I had basically acclimated him to that tank by accident years ago because I had to keep moving him up in tank size...it got to the point he just kept going into warmer tanks until his current tank the 500gal, but the lighter guy is in 78*f tank...this could possibly be the color variation due to temp...but not 100% as the one I have in the big warm tank has alot more mottling and less of saddles. years ago I had a yarrelli from you that I passed on to chad(AP) that was more tan and rust colored with distinct black saddles...so yes definately variation,but as to origin I cannot tell from looking at them...one thing I have noticed between the yarrellis and other bagarius is yarrellis develop the white sensory strings(for lack of a better term) from their snout all the way down their body and as they grow larger so does these strings.....I have kept b. bagarius and suchus and neither had such pronounced sensory nodes.
I have not mixed these two yet...frankly I am a bit afraid to do so..both are hard hitters when it comes to feeders passing by them and both are at the size now that they have some formidable teeth...lol I am planning on possibly trying them together in a 300gal together,but still am unsure of the outcome...I have kept smaller ones(under 9" )together without problems and I do believe these larger ones can be together also...they are not predatory in the sense of hunting fish down...both of mine are sitters and wait for fish to come in head range...so I think if they have room to stay out of each others way they will be ok.....I hope..lol