Honestly you should consider using fake plants....if you do manage to sucessfully grow your aloe it would definately outgrow the space...they get enormous. Don't mean to be a debbie downer just being realistic. Artificial ecosystems perform better in jungle type environments with active microbial life in the substrate.

As Viper said ... for a desert theme, stick with fake plants or dried ones dyed with a food grade dye to look like living plants. Cacti/succs are mostly from arid regions. They do not do well in terrs -- the humidity is too high, air circulation typically poor, light at the levels they require too difficult to supply without overheating the terr and killing the plants and animals in them, and too difficult to water without overwatering.

Know it is not the answer you were hoping for but this is, unfortunately, the way it is.