listless betta

Question
I have had a beautiful betta for a few months now, happy
and lively in an approx. half-full gallon vase that I use
as a tank. As my house isn't so adequately heated, I was
afraid his water was getting too cold (high 60's farenheit)
and so my wife today bought a 2-15gal water heater. I
called up the company to ask if it was okay to put in a
gallon tank and they said it was fine. I arrived home this
evening about 6 hours after I put in the heater and filled
the tank almost to the top with water, and he is just
sitting at the top listless and barely moving (but not
turned on his side) and after pathetically trying for a
food pellet and missing once, he gave up trying to eat it.
Are there any emergency measures I can do to save him, and
what might have caused it?

Answer
Hey :)

Did you just plonk the heater in when the betta was there?  

If you did, it is the shock of the temperature which is making him lifeless or did you top up the water without conditioner?  Because this can cause him to act like this aswell.


Jack