Listless Betta Fish

Question
I recently bought a new 1.5 gallon tank in hopes of having a few fish in there.
the tank came with it's own light and filter, i also purchased some blue gravel to put in the tank.
the night i purchased it, i washed the gravel and i filled it with water and let the filter run through it for around 3 days.
i purchased 1 betta and 2 goldfish to put in the tank.
i also purchased ammolock, stresszyme and aquarium salt to put in the water.
the filter was too powerful for the fish, swirling them around in all directions, so i switched it off.
within a few hours the 2 goldfish had died.
the girl at the pet shop said it was due to overcrowding.
she tested my water and all was fine except for slightly elevated levels of ammonia in the tank.
she also examined the betta fish, who was listless and hanging around the top of the tank, and she said he was fine and to do a full water change.
the fish however still was listless and hung around the top of the water not moving and barely breathing.
within 3 days the betta died.
i returned to the pet shop and she exchanged the dead betta for a new one.
i once again did a full water change and rinsed the gravel very thoroughly. the water turned blue from the dye of the rocks, something it hadn't previously done.
i rinsed the gravel many times til they were very faded and the water ran clear.
i then put 1 drop each of ammolock, stresscoat, and stresszyme.
i put the fish in the water where it swam around happily.
but no bubbles or flaring.
the next day its movement had decreased and its fins were clamped.
it now hangs around the top of the tank like the last fish and i am afraid it will die.
i have since done a 30% water change and keep the water around 80 degrees through the use of a desk lamp.
i plan on buying a 7.5w heater to maintain the temperature with out stressing him out with a lamp constantly on.
i do not have any ammonia or nitrate tests to check myself, but i have a pH test and the pH is fine.
i have also included links to pictures of the fish on the first day (when he looked fine) and then on the second day (where his fins are clamped and acting listlessly)
Day One
http://img.photobucket.com/albums/v351/Silverfox250/Day1.jpg
Day Two
http://img.photobucket.com/albums/v351/Silverfox250/Day2.jpg
(sorry the pictures are blurry, they were taken with my phone)

what could possibly be wrong with the fish?
i have only had the fish two days
i dont want to have a repeat of the last fish.

sorry it's so long but i wanted it to be as detailed as possible.

Answer
Hi Nikki,
Thanks so much for the info and the pictures. I got the first one to work but the second picture link didn't go through. I think your problem is just the elevated ammonia levels. It can do severe damage to fish. I would try doing larger (more like 80%) water changes and making sure the gravel is clean. Keep the temperature consistantly warm and stable as well. Good clean water and warm temperatures are the best thing you can do now for your betta.

I really hope he does OK. What may be the problem is the size or frequency of the water changes isn't enough to keep the fish in good condition especially since the ammonia trouble. There must be something wrong with the water conditions and I bet water changes will help.
Try the massive water changes for a while and see how he does. I'm really sorry about all the trouble you've been through and I hope things improve soon.

Best wishes,
Karen~