The species that I posted are all smaller, 4" or less and no more aggressive than a Ram or Kribensis. Putting all Sunfish in one little box as far as captive care is nonsense. Fwiw the Bluespot would be the most peaceful, but they prefer calmer water so if you're adding the extra filter the others are better choices. As far as qt, it's always a good idea. All of those are available from time to time on AB, or from The Aquaculture Store, www.theaquaculturestore.com. Paul Sachs is a great guy to deal with.I wouldn't, they get too big to go with the gobies and are quite aggressive. I would look into some of the more rare danios, the kind you would have to order from a breeder online or something.