Another past tank - a 15 gallon divided 4 ways with plastic canvas mesh. Canvas mesh also on top to prevent jumps. Each section has caves, a plant and hamster tubes - many bettas I've owned have loved playing in the tubes.
You should never use pvc tubes this small even for a dwarf hamster, they can get stuck and it will be very hard to retrieve them. you should always use the next size up in inches not (centimeters) for pvc water pipes as hamster tubes.
Ferplast FPI 4812 Space Tunnel Mixed Colours Clear straight tube accessory for small pet cages. Size: (approx) Please note: You will receive a random color from an assortment. The color you receive may not be the same as shown in the image.