Doubt it. They need cold water, 65-70. Bettas need 78-82. Newts can get sick in anything over 75. The water needs are different, and are very very dirty, you'll be doing a lot of cleaning. They also only take 1/3 a tank of water, which might not be ideal for a betta. And newts need water and land, and you can't forget, they can climb.
Most important, newts eat fish, and some can grow 6-8 inches long. A betta could become a snack, and the betta could nip at the newt, because of it's bright side and belly colors. In higher temps, a newt could develop an infection from these little bites.
Last edited by MollyJean; 01-21-2010 at 01:22 AM.