I believe the 18" 18" 24" is 33 gallons, according to the company and sites for calculation.

Not that this has much to do with the OP since they have 4, just wanted to chime in.

If you meant otherwise I'm curious why only one could be in there? I have the same Exo Terra but I have only one (no plans to get another) and am curious.

-Alyssa

@rainsrockinreptiles