Choosing the right soil for your aquarium:

This is a medium on which an organism develops, and therefore our famous cleaning bacteria necessary for life in the aquarium.
It is necessary to define the substance, the material, concerning this surface layer of the soil. It is a necessary element for axolotls: on the one hand it avoids the reflection of light on the glass wall of the ground, and on the other hand allows a grip for the small very thin legs of the axos (legs you may have noticed not equipped for running) which prevents too much strain on the little developed muscles of the kitties. Another aspect remains the general aesthetics what could be more beautiful than an aquarium with a natural background and allowing the planting of many plants.
As an aquarium is a microcosm, you might as well reproduce natural settings as much as possible.
On the other hand for young axolotls of less than 10 cm it is better to avoid the presence of any soil quite simply because it could cause an occlusion. The sansibar being ultra thin does not pose a problem, however.
This concern also arises for older children with pebbles and pebbles. The axolotl has a huge mouth opening however the cloaca does not have as much margin, which clearly means an occlusion for the little cabbage. It eats its food while sucking it is therefore regularly found with sand in the stomach so as much to ensure that the grain size of it is suitable, a grain size less than or equal to 2 mm seems perfect. Larger chippings may emerge but create micro lesions on the intestine or even the stomach walls.
Do not put anything under your sand as you can often do for fish, neither fertilizer nor peat, nor all-in-one substrate for that matter, because this is harmful for axolotls (some create agglomerates and others contain iron destroying the liver of axolotls).

Choose your soil

Avoid vivarium sands, used for reptiles and various lizards, they are not intended to stay underwater diverting them from their primary use can lead to negative effects on the material which can disintegrate or distribute in the water of harmful elements.

Some examples of recommended and not recommended soils ...
fine sand that you will easily find at a pool specialist.
The sand used for the filtration of the swimming pool pumps is perfect and economical since the 25kg bags can be bought in various DIY stores and at swimming pool specialists for around 8 euros.