Honestly, I don't think the Baby BiOrbs are the best habitat for my bettas. The bigger BiOrbs are great and I LOVE my BiUbe. But the 4 gal BiOrb has just as much of a bubble current as the larger ones so that can bother some bettas, especially smaller juveniles and females. Also, keeping a heater in the BiOrb is awkward, even with the heater holder they sell to keep it in the orb. It's just impossible to hide the heater and the cord coming out of it. I haven't even bothered to set up my second Baby BiOrb.
The BiUbe takes up the same amount of desk room as the Baby Biorb, but it has more than twice as much volume due to being a cylinder. So you could keep a fish and some shrimp and snails in there without pushing the bioload too far.
Or if you don't want to go that big, the Tetra Crescent Kit is my favorite tank, available in 3 gal and 5 gal versions: http://www.amazon.com/Tetra-Crescent...tetra+crescent
It includes a filter and a fantastic LED light in the kit, so it's a great deal.