There are 29 gallon tanks that are 30 inches long by 12 inches wide and 30 gallon breeder that are 36 inches long by 18 inches wide. How long and wide is your tank? 36x18" should be the minimum you could keep an adult in but most people eventually graduate to slightly longer and wider. If you rae indeed running out of room, I would venture a guess that you actually have a 29 gallon tank.

For example, two common enclosures:

Exo Terra large terrariums are 36x18 x either 12" or 18" high depending on the low profile or not.

Animal Plastic T10 enclosures are 4 feet x 2 feet x 15 inches high.