A couple of other comments, too.
Before I bought my tank, I did a lot of research on acrylic and glass. At first I decided for acrylic. But after talking to tanks owners, I found that acrylic was easily scratched, and with the sharp edges of live rock, this was often a problem. Then algae would grow on the scratches. Also, it was more expensive and there was less choice of tank sizes.
Some further research revealed that about 90 percent of the reef keepers on big websites had chosen glass. Colin, too, advised me to choose glass. I'm glad I did, because when my octopus became an adult, she was prone to moving the live rock and scraping it along the glass.
Also, although our TONMO ocotopuses have lived in tanks of many shapes, if you have a choice, it's probably better to have a tank with a larger footprint and and a less tall for an octo.
Nancy