IMO, DON'T GET THE TALL TANK unless you are a glutton for punishment (not a problem for the octo). I have 3' tall and 4' tall tanks and cleaning them is the pits. When someone is looking at tanks I always recommend checking to see if you can reach the bottom as the tank will be set up (so in some cases this includes a hood height).
I am glad the lump is a camera artifact as it worried me a bit. I am wondering if it caught some of the biologics though. I will be glad when you make a good sex ID to see if there is something to the candling affect. Based on that thought I am guessing female but we have not seen this effect before so that is just an impression. The arm you want to observe is the third arm to the right clockwise as you position your eyes with the octopus'. None of the other arms (in all most all cases, there have been some odd exceptions) are going to tell you anything. Losing an arm does not change the biology and the hectocotylus will have a channel running the length of the arm (more easily seen in photos than with the naked eye). The tip will regrow without suckers and have a different tip but the biggest give away will be that the arm is usually carried rolled up. We named SueNami when she came with the third arm completely missing. As it grew back, it was clear we had a boy named Sue
Initially we conjectured that this arm was the most protected so the octo must be female, later we decided that he may have lost it in a mating attempt. All second guessing of course
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The regrowth of the arms should be a very good interest point for the kids, especially if you can get her to feed when they first come to class in the AM as you should ultimately be able to get her to reach for the food so you can see the arms thicken and catch up to the others. The octopuses that come from Tom are usually brought in from crabbers and this is stone crab season in the Keys. If you have eaten stone crab claws, you will note that they are quite strong and can intuitively understand why the octos are in arm regeneration all the time. Additionally, when you see this species hunt, it is clear that they lose their arm tips to anything hiding in the rock in addition to natural predation instigated by other animals.
She will take awhile to start coming out but live food will help (in addition to a regular feeding time). If you can get your hands on a live shrimp or two (bait shop is your only bet here I think. They should survive fairly well in the other tank and not be too hard to catch) you will likely get a nice show of the webbing and full body. If you will go to my YouTube channel (
dwhatley_GA) and search for: shrimp, there are a couple of videos of this species attempting to or catching their shrimp dinner. This species seems to have very far sighted vision and does not see well close up so the shrimp allows them some hunting time in close quarters.