Decor and Hides
As a general rule of thumb, each axolotl needs at least one hide. Axolotls LOVE to hide. A hide can be anything from a PVC pile elbow to a custom piece of pottery. Many owners like to use terracotta pots. My favorite type of hides are ones that look natural. You want to be sure that whatever you are using is aquarium safe and does not have a painted surface which can degrade and leach into the water creating an unsafe environment.
We have found many great hides for sale on Etsy. One of my favorite shops is called "Hot Flash Pottery". They make beautiful hides designed just for your pet and they have proven to be safe for axolotls and other amphibians. They can even create a custom piece just for you and your axolotl.
We like to load up our aquariums with tons of decor in all different heights. We are currently using fake plants, river stone, and fake moss balls. We like to use tall decor to hide our filtration and chiller tubes while also giving our axolotls the ability to explore the entire tank. We do note them climbing the plants and making their way to the very top despite spending most time on the tank bottom. It's nice to give them the option when they want it. Remember, your stones should be at least twice the size of your axolotl's head in order to prevent accidental swallowing. Large river stones have proven to be great!
Many people prefer to use real plants. This is also totally acceptable. Real plants are excellent for helping out with your water parameters and provide a natural form of filtration. However, you want to keep in mind that plants need light to survive and axolotls don't like the light. Be sure to choose plants that don't need a lot of light. Ideally, you only want to keep on a light for about four hours a day if you have to for plants.