They get 7-12" and really only need a 20 gallon.
The one on LiveAquaria is really, really overpriced for that brown color. I don't know why, but LA has really been pricing things outrageously lately- even more so than usual.
My dwarf ate my pistol shrimp, and I wouldn't except them to pass up small gobies. Other than that, they're basically reef safe. Larger cleaners, blood shrimp, coral banded shrimp, etc, are likely safe. Their mouths are small.