:O :O :O
Hun, you are gonna want to get a bigger tank! The minimum
amount of gallons any heater can heat without cooking it is 1g. And heating pads are kind of sketchy-- they're not designed to support the weight of water, which is 8lb/gallon.
Also consider that at the rate a betta fish produces waste, you need to clean a 1 gallon tank every 2-3 days, so for a 1/2g that would mean daily cleaning! Not to meniton your betta is going to need some room to swim around in order to stay in shape! I strongly suggest you look into a bigger tank. Here's a little blurb I wrote for someone else who was struggling with tank size a while ago:
A lot of betta owners really like the Aqueon Mini-Bow 5... I would check it out if I were you. Great little kit.
Yeah. Unfortunately fish stores will sell you just about anything to get your money. And they make considerably more selling cheap tanks to a bunch of people than they do selling proper tanks to the few people who have actually done their homework on tank size.
Another common myth is that small tanks are lower maintenance. If you put three drops of red food coloring in your 1g bowl, it would probably turn the water bright red. If you put 3 drops of red food coloring in a 5g tank, it would only turn the water a light pink. The same goes for the waste your fish produces. The smaller the tank, the stronger the waste will be. So you have to clean it more often. If you are looking for a truly good beginner size, I strongly recommend you grab a 5g tank.
Furthermore, there are no heaters on the market that will heat a 1g to the right temperature. Since it is such a small amount of water even the smallest of heaters will often make the water too hot.