White-ish slime coat on top of water?

[Kristene]

I have one crown tail betta in a 2.5 gallon tank.. I change his water every Friday with a bottle of spring water I buy at the store and I've had him about three months now. I bought a live plant and have had it out this past week thinking it may have been a sorce, but the slime still is on top of the tank.
I read the FAQs here and whatnot, I have no heater, I don't test the water nor do I have a filter on him and I feel terrible now! Like I've almost been abusing him, but I just didn't know.
I have him sitting on the window ledge of my small bathroom because it stays warmer in there then in my bedroom, he has no direct sunlight on him but is lit throughout the day by natural sunlight.
I've been feeding him tetra freeze dried bloodworms and I'm looking into buying a heater/filter, I'm a broke college student though so it may be another week or two.
He lies on the bottom of the tank half of the time and the other half he spazzes out and jerks around the tank. He no longer puffs up at the sight of himself in a mirror either. I don't know what's wrong but I want to fix it so badly! It's been going on for a month now and I want it stopped.

Any help is welcomed, please pass on any information you can offer me.
- Kristene

[dramaqueen]

Hello and welcome to FishForum. Your betta needs a diet of more than just bloodworms. He needs a good pellet food for his staple diet. You can can feed the bloodworms as a once or twice a week treat.

[Kristene]

Thank you very much, and i will keep that in mind. Good thing I bought some pellets :)