I bought a little breeding tank (which is supposed to float in the main tank) for the female fighter. It gives her more space and ensures that she has clean water (or, well, the benefits of filtration) and warm water. Hopefully I can let her into the main tank once the fry get a bit bigger. I bought a heater for the other tank, but it turned out to be too big for the little tank (the heater is as tall as the tank). I feel pretty sure that the other fish is a short-finned male, but I may be wrong. Anyway, for the time being, the water temperature in there is ok (I bought a little stick-on thermometer), so hopefully he'll be fine.
Looking at the 'Bettatalk' website, it would seem that trying to breed "petstore bettas" is a horrible idea that is bad for me and bad for the species. But, the truth is, I'm far more interested in breeding fish, not raising generation after generation of "superior" fish. I'm not going to be a professional breeder, and if I am (a) I'm going to learn how to breed and raise the fish before I get into specific strains, and (b) I'm a big fan of "mutts" and of trying to see what they may have to offer.
We got pretty close to buying a new tank today. I think we could fit another 10 gallon tank, and a full kit runs around $50, which isn't all that bad. It could work as a quarantine tank, or as a breeding tank for fighters - or both, if I clean it up well enough in between. I'll see what happens. I suppose I have a heater to return. I'll make a decision in the next day or two as to whether I want to buy another tank and setup. What's really sad is that I can get the tank (sans all the other stuff) for just $9.00 - that would be enough to breed fighters at home, but here you can't run a tank without a heater. Oh well.