The best I've had is my flagtail. He's been doing such a good job, I just got another baby a few weeks ago. I've now got one that's about 7" and the new guy is a little under 3". The only problem with these guys is that they get BIG and are fast when spooked. Right now, the bigger one is in a 150 and the little guy will be moving into my 75 in a few months. They aren't particularly fast growers, so I've got a while, but they'll need bigger tanks in a few years.