Sulcatas are the third largest tortoise worldwide. Greeks don't get as big as them. Greeks and Hermanns can reach 14-15 inches max. I don't let my dogs near my torts, though they seem real curious.
A sulcata hatchling could stay in a 55 g for less than a year. Or, to go a cheaper and easier way, get a rubbermaid that is that wide but short. It's inexpensive and safer for the tort.
Torts like to roam around and if they see through the glass of the tank, they will want to escape and go further. But they can't see through rubbermaid.
But sooner or later, you'll be forced to build an outdoor pen.
And if you are going to get a sulcata, plan ahead before it gets so big you can ride it
