Hi I believe that an adult pair can be housed in a 10 gallon tank.

I was reading a care sheet from Pro Geckos, and he said a 10 gallon , of course bigger is better, or if using a rack system he houses adults in a 26 quart container and youngsters in a 6 quart container.

More people may want to jump in and add some info or what they may use, but if using a tank I think I would go with the 10g if you get a little guy, and maybe go bigger when he's older. Best wishes, let us know what ya get
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PHEve / Eve