3 Bettas and I need heaters!

Question
Okay so I have 2 male Bettas and 1 female. I learned
recently that Bettas thrive in 80F temperatures. I have
them each in their own little 1 gallon tank currently and
they're all pretty happy but I know they'll be a lot
happier in their homes if the water was warmer. So what I
wanted to do was to get a 10-20 gallon tank and put
dividers in the water. My only worry is that my Bettas will
flare all day long and get stressed or something. And I've
read that you can replace the clear dividers with perforated vinyl siding from HomeDepot but I don't
necessarily trust that because that isn't made for fish. My
question is; Is there anything I can do to change the
dividers a little so the bettas can see each other
sometimes but not ALL the time. (Kind of like this tank: http://www.arcatapet.com/item.cfm?cat=8916) But that tank
is too tiny and you can't use a heater with it.
Another question.. if I can't get anything for the Bettas
to see each other only sometimes, can I put my female in
the middle? It seems like my males don't flare up at her as
much, but she'll flare at them from time to time. Thank
you!

Answer
Hello,
If you get a 20 gallon tank, you would have enough room to add tall plastic, or silk plants against the divider so that they don't see each other.  Betta who see each other all the time, will get very stressed, and sick.  The little female stuck between two bettas, isn't good either.  She would be living in fear all the time.  I have seen pretty bushy plants that would cover the side's of the divider, and it looks really nice.  You could also get flat rocks, and push them against the divider, as long as they are not rugged so that the bettas don't hurt themselves on them.  Plants are better.  I don't think they would try to get in between the plants, they would most likely avoid this, but ask another expert, they may have better ideas for this, as I have never used dividers with my bettas, but can see the problem.  I was thinking too, of coloured acrylic sheets that they could not see through would be good also.
I just want to mention that when you do heat the tank, put your bettas in the tank with the same water temperature they are in now.  Raise the temperature one degree every two days.  The temperature must be raised very very slowly, as raising the temperature too fast could kill them.  This is very important.  Bettas do need a heated tank.  They are very unhappy in cool waters.  They are tropical fish, and 80 degrees would be heaven for them.  In their habitat, the water may be shallow but they have lots of room to swim.  It's so sad to see vendors selling bettas, and telling the customer that they do well in small bowls, tanks, vases etc.  When living in these conditions, the bettas eventually get sick, and the poor customer who got attached to his bettas, does everything he can to save them, but often it is too late, and the betta dies.  It's a money making machine, and it just boils me over.  I'm happy to get questions like yours, because I know that you will take good care of them.
Hope this helps
Lynda