at under 25C they are likely to get stressed and develope cold-water diseases like Ick so deffinately need to be kept between 27 30C, to breed bump the temps to at least 29C. get yourself some ketapang leaves, also known as indian almond leaves, thats stuff is available at petshops but its stupidly pricey so just import a huge bag through ebay (quaratine will open the package but they're dead dried leaves so they'll make it through) they then soak in the tank water or you can boil them to make a tea to change the tank water conditions to something more similar to the bettas original habitat. they might not be making bubble nests because, ironically, the water is too clean, so not sticky enough to hold the bubble structure. now dont think that means you can stop clenaing the water!! just get your hands on those leaves and they make the water lovely and sticky, will make the tank look feral though
a bit brown and dirty but thats just the tannins being released which also help as a natural antibiotic.
so, 1. get the leaves for the water
2. temps to 29C (tank MINIMUM of 20L, althougha 1.5 - 2 foot tank is recommended)
3. give the male a nest site of bubblewrap or a styrofoam cup so he can build his nest there and it will be protected from condensation.
4. keep the lid on the tank to keep the air moist - IMPORTANT
5. condition your fish, lots of live blood worms are best - female must be conditioned for 2 weeks for best results, she will look like shes almost popping with eggs (be careful not to overfeed though)
6. learn how to intro them, you dont want your girl to just rip your boy up straight out, and learn the body language otherwise you could kill the female from stress alone (body strips, head-down, wiggle etc)
also, they breed with wet weather, and winter makes it alot harder for them to get in the mood so i would wait until september... get a heap of duckweed and javamoss - helps to feed fry and keep the tank nutrient load down
loads more info at ausaqua.net