Select from options: Continue writing the next sentence.

How to make a millipede habitat
Select the right size container.
A glass or plexiglas aquarium is ideal for housing millipedes. You can find one of these in a pet store.

OPT: 1. A 3-gallon (3.8 l) aquarium is a good size tank to make. It is best for 6-10 millipedes, a larger tank 6-10 millipedes, a larger tank 13-20 millipedes and a smaller tank 10-15 millipedes. 2. That being said, all millipedes grown in captivity should be at least one meter in length. They should have a clean surface, such as a glass or plexiglas tank. 3. The container should also be wide enough so that your millipede can hop into it comfortably without getting injured. Choose one that has sides that are equal in diameter to one inch (2.5 cm) thick. 4. Such a tank will allow you to easily observe the millipedes and control the lighting. Plexiglas (hardened transparent plastic) will be lighter in weight, so this may be the best choice if you plan to take your millipedes along with you now and then.
Answer:
4.