I have a 110 gallon reef tank would that work? I would have take fish out and remove my torch coarl and maybe others. My husband won't be too happy if I get one more tank, I have 3 now. I may up grade when he gets bigger. His body is only 2" and about 10" from tentacles across. He does have great personality!Well if he is a Vulgaris then I would guess 4-5 months. Hard to tell with out a size reference. Someone else took a pic with a quarter up against a tank which helped a lot. 32g is not going to be big enough. Just so you get an idea of what you might have check out "Into Casper" You will see that when I got this octo I thought it was a full grown dwarf like a Merc. But the activity and how much she eat made me think other. When I got Casper she was quit small but grew extremely fast. I got her Oct 10 of this past year. She is in a 93g cube and just bought a 6' 150 system because she has outgrown the 93g cube.
Now D will "I think" agree that Caspers growth has been crazy fast and she is larger now then others Vulgaris ever got. "some stay smaller then others" Check out "Little Bit" and you will see one that didn't grow to be so big. Again all of this is just a guess because we are not sure its a Vulgaris. Mind you if it is you have one of the most sought after octos in the hobby because they are very outgoing and are out during the day.