Haven't seen them in a couple of years (except in my tank)... I have a male t. sp. "xingu".
I've tried these guys twice. First time was in Sacramento when I picked some T. monogramma up from a LFS (!). I got a trio. All was well for about 3 months...until the male decided he wanted to breed and destroyed the first female and then the second. I tried to keep the lone male with some other small South Americans...but he was too worm-shaped to resist and was eaten.
The second time, I got 3 T. sp. "xingu" from Julie at Frybabies. Same thing happened, despite the tank being large and filled with PVC. I still have the male, who's now pushing 3.5", monstrous for these guys.
They'll lull you into a sense of success, until one day you'll find the shredded remains of one. The males are absolutely brutal on conspecifics.
Matt