Sorry for the loss man, perhaps it's like they said and fish have no personalities but IMO every fish I've owned has been different and I mean the same breeds and ages over the 12 years I've been doing this. I have had a complete success at what you were trying to achieve as I've shoal'd gatf/vatf and payara for a long time now with nothing more than a few scales missing here and there. I have plenty of dithers being polypterus and snooks to even Indo datnoids. My tank has little to no aggression unless it's feeding time. Oh forgot to mention I've also successfully introduced a mala wolf over a few weeks now with not even one territory incident and everyone is happily getting along together... But like they said some people get lucky. It's all about environment from what I've seen, when they are limited to swim space and have low current they become intolerant of eachother but when open space is available and extreme overkill current they are gentle as babies. Just my personal experiences with these guys not trying to disregard the pros who were speaking before.. Just for the record I've lost a gatf before due to fighting (a few years ago) but when the correct environment is in place you'd be surprised. Just my two cents 
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