Yes, I wouldn't advise keeping them with angelfish. Plus they enjoy the perks of some brackish minerals in the water. I have them with caranx sp., lutjanus sp. , epinephalus sp., centropomus sp. and there is not much aggression.
Wes could I please see some more pics of the Pseudauchenipterus nodosus? They look to have a broadly similar body plan to Ictalurus furcatus, without the unreasonable size. Google isn't much help.
I have one picture from the fisherman. I'll have to take picture of the one I have left. They swim around when they feel comfortable, and hide when they're scared. They'll eagerly scoop up cut bait as food. I have a small one 4" big, he will come out and eat until he's puffed up then go hide.
These are caught in the upper Courantyne River, Suriname.