Megga, make sure you let your water sit for a day or two before you add your fish to it. Also, you can get some 'stress coat' or water conditioner that will take out harmful things like chlorine and chloromine from the water. I still let my water sit before using even though I add the conditioner.
Goldfish are very dirty fish. If you have them in a small goldfish bowl with no filtration..they probably woulnd't last long....although...I do know someone who has two goodsized ones in a gallon size goldfish bowl, no filtration and they do fine. But she boils the water and lets is sit before water changes...and she does changes frequently.
Make sure that you allow your betta to get used to the new water. After you have let the water in his tank/bowl set for at least a day...float him in his new home in the cup he probably came in. This allows the water in the cup to reach the same temp as the water in his new home. After about 15-20 minutes..add a little water from his new home into his cup. Do this slowly and take your time getting him used to the new water. Even if you let him float for a day or so, it won't hurt him to stay in that little cup a bit longer, especially since you are adding new water to it.
If you take your time getting him used to his new home and you keep his water clean and don't overfeed him, he should do fine. Good luck and let us know how it goes! <img src="/images/graemlins/wink.gif" alt="" />
