Hi systemmatic - sorry to be a bit late catching up with this thread! I have a BiOrb, and rather than follow the instructions that came with the tank, I took Goldy's advice and cycled my tank for a month before I added my first fish: a lovely telescopic fantail called Goldie! He has huge white eyes. Then I did water tests and in a fortnight, added Serpie and Scales. I have a very good fish shop, and the guys there said three was enough - they're small at the moment but I know I'll need to buy them a new home in a year or two. I have three plants in with them, and do a water change every 10 days; filter change due this weekend. I only know about fancy goldfish, but can highly recommend telescopics, as they are soooo cute!