New Betta Aquarium

Question
I have 2 separate issues. I recently bought a male betta and he
has been in a 2.5 gallon aquarium with a rock and various
plastic plants for about 2 weeks. It has a 15 W incandescent light
over it and the water stays about 70 degrees. When I first
introduced him to the tank he swam around happily and ate
well. For the past couple of days he seems lethargic. He will eat,
but seems far less interested and has spit out the food. He
seems to sit at the top of the tank right under the light, but he
does blow bubble nests. Today I noticed that his face may have
some slight discolorations. I am just wondering if he is sick and
what I should do about it. If I medicate, does it hurt him if he is
not really sick?

Also, I want to keep him as happy as possible. I am worried that
the water temperature is too low for him to be comfortable. I
realize bettas can live at low temperatures, but would prefer
higher temps. I have a submersible heater in my 20 gallon tank.
I am wondering if it is possible to put a heater in a 2.5 gallon
tank. I was thinking a 25W heater, but I don't want to cook the
little guy.

Thanks for your help.  

Answer
Dear Marcy,
You could certainly be right about the low temperatures causing your betta to be listless. Is there any way you can move him to a warmer spot in your house? Oftentimes the incandescent light will keep the water warm but if your home is kept quite cool, this isn't always the case. Fortunately there are small heaters made specifically for small aquariums of a 2.5gal size.  Just go to-
"Bigalsonline.com"
and Type in the search box "Mini heater" and you will be taken there right away.

I wouldn't try to use a 25watt heater as this could be a very dangerous situation. If you can get him a specific heater for that size aquarium that would be excellent. I don't use heaters too often myself except in wintertime as I keep my house at a warm temperature all the time.

I don't think he needs medication. And it's best not to medicate when you aren't certain of any fishes illness. I think what he needs most is a warm temperature and if he were mine I'd do daily 30% water change everyday on his aquarium. Always remember to make the replacement water equal in temperature to that of your aquarium and insure to dechlorinate it everytime with a good water conditioner.
Do these water changes until at least he improves. It could also be that poor water quality is making him feel bad. Like ammonia or nitrites in his aquarium water due to this aquarium being newly setup.

I really hope this helps!
Feel free to write if you have anymore concerns and Best wishes!!!
Karen~