It's always better to have a bigger tank, but you probably won't necessarily need to upgrade "soon." They have the possibility of getting a foot, etc. but they could take a few years in some cases, before they're full grown.
And I also agree that it's swimming motions are normal.
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If you put "u" instead of typing out the actual, shocking, three letter word... i'm not going to read your ramblings.
I'm so behind it's not even funny.