Swordtail characin
I got a big group of these from Randy Carey and they were very happy and vigorous in my soft water. Much like a farm-raised tetra they eat anything and seem determined to flourish. They tend to clump together in a small area, not exactly schooling but constantly turning and chasing each other. This is probably in part due to the weird gill-plate lures that the males use to angle and bait in females.
Randy told me that these were internally fertilized, so my first spawning attempts involved isolating a single female over a grid. These fish are VERY fast and elusive, so scooping out a single plump female from their tank took a surprisingly long time.
I never saw eggs or much activity in the special-purpose spawning tank. Eventually I moved a lone female into a full planted 10-gallon, and that did the trick; lots of fry showed up after a week or so.
Later on I moved the whole group into very weedy 25- gallon tank with some ancistrus, and that tank now produces new fry regularly without any intervention on my part.
I don’t think these will ever make it as a commercial species because of their pale colors, but they sure do put on a show. I’m not sure why this species is a ‘characin’ and not a ‘tetra’ since ‘tetra’ is already a pretty broad, ill-defined clade.