A 30g is what is recommended, this lion reaches 6 - 8 inches, but it will not reach this size over night, lions are messy fish and create quite a bio-load.
With that said, you can put a zebra lion into a 30g and probably for a few years, just don't over crowd the tank with other fish, especially other fish that are messy, your tank may fall into trouble if you do this.
Kaye