No, they grow just as large if they are kept in a healthy environment, (if not kept in a healthy environment they won't live long enough to reach that size...

) Many keepers have large ponds for the summer months, with temporary winter quarters indoors. This is good if you have the climate for it.
Another option that's good are stock tanks. They can be gotten from feed supply stores and are much more economical than glass tanks.
BTW, at that length 10-12 it sounds like "he" is she. Female RES grow to reach between 10-12 inches, while males only reach 7-9 inches. Also, females have short stubby front nails with a shorter tail while males have very long front claws with longer thick tails.