thick resistant white fungus on betta

Question
I inherited a beta in a l gal tank from my daughter.  It has gravel in the bottom, a small tank heater, a curved rock thingy he can hide under and three floating plants.  He now has a thick white patch of fungus on his belly surrounding his anus?  I read thru all your answers and now see that I need a larger tank and that I was feeding him too often and not changing the water often enough.  My problem now is how to clear up the fungus.  I am now changing the water weekly, I am adding 1/4 tsp aquarium salt and a small piece (they are designed for 10 gal tanks) of the Jungle Tank Buddies Fungus Clear dissolved in water with each water change- which might be keeping the patch from getting larger, but in no way is it clearing it up. I have also added another piece of Fungus Clear about midway thru the week when I see the patch starting to get bigger.
 I live 1 1/2 hours away from the nearest pet store so I can't get a bigger tank until I get back there.  What can I do in the meantime?  The only other thing I have on hand is Betafix.  I turned off his tank heater last night thinking colder water would slow the growth of the fungus. This has been going on for about a month now and I am getting no where.  I totally don't know what to do next so I am hoping you can help me.  Thank you!
Kathy

Answer
Kathy,
This first thing you should do is turn his heater back on. He needs his water to be 80 degrees at all times, after all he is a tropical fish. The salt in the water will help. The ratio is 1 teaspoon of salt per gallon of water. The Jungle products are very good, so I would continue doing that. I think that if you continue the medication, add the salt, turn his heater on to 80 degrees and keep his water clean, he should start clearing up. Since it took a month to get this far, it will take a little time to get him healthy again. Keep an eye on him and let me know if anything changes.