Two main rules with Axolotls is that they are big waste producers and need cool water. They can also be territorial towards each other, but don't worry any limbs bitten off will regrow, the same with chunks bitten out of tails and their feather gills. Speaking of gills an Axolotls feathery gills should never be sparse or clamped looking.
It is good that your thinking of using sand because adult axolotls can be prone to eating small pebbles with can cause intestinal blockages. However if there are baby axolotls they require small pebbles otherwise they can have the same problem with ingesting sand. The jury is still out on the hazards of gravel, you could try using some largish smooth fish gravel of just use a floor of tumbled stones that are often used to put a nice rock cover on potted plants potting mix, or set into concrete paths.
Now I will get the confusing thing about axolotls out of the way, what we see as "adult" axolotls are actually still the tadpole form of the true adults but and its a big BUT these tadpoles unlike any other tadpoles eg frog/toad they can breed in tadpole form.
Feeding axolotls can be very stubborn in only accepting live foods, and will often hand feed. If you can get them to accept specially designed pellets they will be much healthier and easier to feed if you are a way for any length of time. As a treat you can give them earthworms and mealworms but limit these treats in case they begin refusing the pellets again.
Plants are fairly important to give the axolotls shade but also if the weed is semi floating they may lay eggs in the weed, as well as calmbering through it and resting near the surface.
Always ensure their water is not too cool or two hot. Too cool and the metabolism will slow down, too hot and the metabolism will speed up and cause stress largely due to the lack of oxygen in warmer water. Aim for around 16-18 degrees Cel (61 F - 64 F)
Because axolotls are big waste producers not only will you require a pretty heavy duty filter (but not necessarily strong back flow/ return) but I would probably look at doing at least two partial water changes each week, being sure to vacuum up any obvious waste. Also vacuum after feeding to prevent any missed food growing fungus. Always be sure to use a dechlorinator on the water too because chlorine is harmful to amphibians especially so since they have only thin skin.
Axolotls should be happy in a pH range of 6.5 - 8 but ideally 7.4 -7.6 should be perfect for them. As for water hardness axolotls generally like hardish water, too soft and you may need to add aquarium salts to improve the mineral content of the water.
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