Two of the diagnostics (asside from the ocellus or false eyespot) of hummelincki/filosus is an arm length of roughly 2.5 times the mantle and a arms that narrow very quickly. I have also noted the peach speckled underside and the purple rings around the edge of the suckers (trim as CaptFish calls it ) to be a common factor (they can show a completely white underside on occassion but typically it will be the peach specking). The ability to turn the "eye lid" (not sure of the proper name for this) red is also common (but may not be diagnostic as I don't know how many other species can do this). I missed a totally evil shot of Octane flashing this from very dark red to white once (without moving any other part of the body) and commented on how scary this might look to a diver. I am relatively certain this is hummelincki and, given the supplier likely from Haiti.
I have also commented on my thoughts that there are two sizes and possibily two related species that fall under this name. The larger of the two seem to have much larger mantles in terms of thickness (width) than the dwarf sized (look at Octane and OhToo and then at Maya and Serendipity). Hopefully you can see that the later two were much more delicate and lacked the girth of the first two.
As far as being active in the tank. What you are remembering is the description of senescence. Hummelincki are day active and you just put it in a new environment so any activity for the next week or two will be acclimation oriented. The behavior you don't want to see is random movement without purpose, breathing difficulties and spiral curling of the arm tips (not sure hummelincki shows the later though). However, even these symptoms in a newly introduced octopus are not necessarily signs of old age. Just accept that you have two weeks to be on pins and needles and take a couple of antacids, it will be like this for every new one you keep.
Well last post for the day. My Octopus (I will provide a name when he/she starts interacting with me) He/she has finally settled on a den and covered the opening with a big shell. He/she also made an escape route out of the back with pvc pipe. I think I may be in love.
I attempted to feed my Hummelincki today. He/She took a piece of shrimp offered from a bamboo skewer at 2:43pm. Here's a photo of the size of shrimp offered. I noticed he was out of his den so I thought it would be a good opportunity.
A lot of the "raw" shrimp we see in the seafood section is suspect. It had not been "cooked" but something has been done to it. Shrimp should not be opaque white. I suspect something like lemon juice is used as a preservative which will "cook" it without heat. If you have the option, try to avoid any shrimp that is white it should be translucent and greyish.