First, i dont have personal experience with Black Widows. But from what ive heard, they kill almost everything.
My experience is mostly green, red, and rainbow BTAs, colorado Sunbursts, chicago sunbursts, lemon drops, and flame-tip/Alien-eye BTAs.
As for mixing, most everything will kill sunbursts. They dont need to touch, but merely be in the same system. Even two nems in 2 diffferent tanks, plumbed into the same sump, has resulted in death. Once started, death is quick and unreversable. Removing a dying nem to a QT system still results in death. Death occurs in minutes to hours.
One of my old (wealthy) acquaintances had purchased nearly 30 Sunbursts, one at a time, for $1-2k each. Because she was committed to a mixed anemone tank, and they kept dying.
I got lucky with mine. My Sunbursts split at the same time my rainbows split. And due to the nature of my apartment setup at the time. I was forced to mix one way or another. Fast forward through the details, my Rainbows did not kill my sunbursts. Yay!!! I later cautiously tested flame-tip/alien-eye with the same pair of nems (rainbow and chi sunbursts), and they got along too! That said, i will not test any further. I pushed my luck and won a couple consecutive gambles. Its only a win if i stop while im ahead.
TLDR: its totally possible to mix nems. But be prepared for a high chance of failure. Use nems that you have multiples.
