Betta dying, listless

Question
Hello,
I am caring for a coworker's Betta.  She had brought him in to the office from her house in a small plastic cup.  We put him into a plastic aquarium, about 5.5x8x5 inches.  We keep the tank under a warm lamp so the water stays about 65-72 degrees (rough estimate).  On the bottom for gravel we use blue glass rocks.

At first it would lie listlessly on the rocks, and suddenly dart around very erratically for a minute or two, crashing into the walls and floor.  Then, it'd drift back to the floor listlessly.  Sometimes, it would keep trying to bury it's head in the gravel until it's exhausted.  We thought we had an insane fish.  We tried feeding it everything including betta pellets, betta flakes, and freezed dried bloodworms.  It takes one bite of any food and ignores the rest.  It's been a week, and for the past three days, it has not eaten a single bite.  It seems much weaker now, and does not dart around anymore.  It just lies on the bottom of the tank, after pushing aside the rocks.  once in a while it'll swim to the surface to breathe (it seems) and then fall back to the bottom.  Today, it does not even swim to the surface anymore, just lies there.. much weaker than before.

I'm afraid it's probably almost dead.  But if there's still some advice you can give to save it, that would be great.

Thank you very much.
-max

Answer
Hi Max!

~So sorry to hear about the poor betta! I will help you out all I can.~

~*It's somewhat difficult to really diagnose what might be wrong with the betta since I don't know how his previous owner cared for him including what temperature he/she kept him at, what he/she fed him, and how many times the betta's home was cleaned. I can say that when he is darting around the tank that could be a sign of really bad water quality such as high ammonia (any trace of ammonia is toxic to fish), or high pH. He may have been shocked by a switchover in water chemistry from his previous owner to the little aquarium he is in now. I'm really sorry to say, but he is pretty advanced as far as stress level goes...you know what I mean?

~65-72 degrees is pretty chilly for warm water bettas. They do best at 80 F but can live pretty well in 73-78. The cold water is stressing him out even more I suspect. I also need to know if you acclimated him to his new aquarium properly. Like did you float him for 15 minutes at least?

Something you can try to do to help him is after setting out a gallon jug (half gallon either) of water that has been de-chlorinated with water conditioner, for overnight so it will equalize in temperature. To use a cup (preferably a betta cup) to scoop out about 20% of his water and carefully refilling the aquarium with your aged water. A 100% water change would probably be too stressful for the condition he is in now... :( Also try to raise his temperature...don't try to do it too fast but like put a lamp with more watts right over his aquarium to raise it to at least 75 or higher. Doing those two things might bring him around.

I hope I helped, if you have anymore questions just email me again! I am more than happy to help you out all I can!

~I am wishing you the best of luck with your betta! I really hope you can save him!!!

Take care, Max, and happy fishkeeping, (hope your betta gets well!)
Karen~