Kept and bred Tucurui, mine were not wild. They didn't require any special conditioning to breed. ..tap water 7.1 pH and 160 microscemen.
I found them not to be an attractive fish..actually, real drab looking (sorry John!).. like John said, the only time that they showed some yellow coloration with lateral lines was when spawning.
But, than again, you know what they say "beauty is to the eyes of the beholder".
Good luck with them.