My Octopus

Actually if you look at the one shot it doesn't look the top has been secured at all with the Orbit light fixture legs on top of the tank..

If you haven't completely secured your tank you should start doing the research.. It basically boils down to anything they can get their beak through, they can get the rest of their body through.. You should talk with Marine Geek who I believe was one of the first people to post about octopus..
 
I believe it to be a male aculeatus, but it is hard to say either for 100%.
I did close the top off with screens i made. I took the legs off the light and use it to hold the screens in place. I dont believe these octos reach large size i would say no more than 18" across but i could be wrong i cant find much info on them besides research on them walking on two legs. i see that junk every where.

DSC00394.JPG
 
AquariaCentral.com