What is a good sized tank to house a bearded dragon?
One size for the baby beardie, and one size of tank for the adult.
Baby beardies do better in a smaller (10 gallon) tank. This way they can find their crickets. Older beardies if it's one in a 20 long or larger.
a 40gal long tank will do it. most of my lizards are in 55gal tanks