Betta Dying

Question
He Is In A 1 - 1.5 gallon bowl. Currently I am trying to save money to buy him a 3.5 tank. He has a desk lamp over him because that is what I was told to do until I can get the new tank that is bigger and could hold a small heater. As for the levels I don't know becaue he was kind of a surprise and everything I had ordered is still in shipping and won't be here until Monday which was when I was suppose to get him.

He has a white kinda of string like thing coming out of his under part by his gills ( this is the first time I notced it). He just ate today after 4 days(peas about 2-4 bits of them my sister feed him so I don't know the exact number). I clean his bowl every 2-3 days. Using Betta water conditioner and letting it sit for 24 hours before. So now here is the question.

What is the white sting like thing there? Why is it there? And how can I treat it?

I have Betta Health Aid Revive that will be here Monday. (Its found at Petco.)

Answer
Thankyou for your revison.

The problem with bettas, is that, because they are sold in cups, people dont think the need heaters, filters, or much space. That is the complete opposite though.

Is the string coming from his anus, or from his body?

let me know

Matt.