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Some how this hobby spurs others, one, out of necessity, being improvement of photo skills (for some it is a full blow additional expense!). Clearer photos definitely needed but you can look for a few clues. This is particularly important for the possibilities here because any other species we normally see needs to be kept much warmer.
What to look for to ID a bimaculoides (not to differenciate between the two bimacs, we just don't see bimaculatus):
1. A pair of Eyespots (ocelli), one below each eye. They will look basically like a bull's eye and can be detected in all but the very darkest of brown coloration. When very clear it will show as a yellow ring, a black ring, a blue ring and a black center but the sharpness and strength of the colors will vary with mood. If there is no sign of an eyespot, slowly bring your temp up to about 75 (it should be below 72 for a bimac and below 68 is better). If you are sure it is not a bimac let it come up to 78.
2. IF you find the eyespots (keep in mind the colors can vary so you are looking for the circles in the right place, not the colors) next, look at the tips of the suckers. If they are a strong orange (not peach), the chances are you have a bimac. If they are white, keep watching until you see a definite strong color. If they are purple/blue you have an O. hummelincki.
If you DON'T see an eyespot, it is unlikely a bimac but still could be O. hummelincki as their ocelli are not always visible. Don't look at the other differences in the two similar species. Just use the photos for the topics mentioned. They can both look very much like each other in some of their costumes (I've only kept one bimac but do think there are some looks that are not similar but they share many of the same textures and colors).
Look at the arms and mantle (the sack behind the eyes, not including the eyes). Using your thumb and pointer finger, try to gauge the ratio between the mantle and the arms (unstretched). Very scientific calculations here
Look at the arms, are they fairly uniform for most of the length or do they seem to taper very quickly?
At the top of the journal and photos subforum, you will see stickies (colored green and always at the top) titled List of Our Octopuses 20xx. If you open any of the years you will find the species (if determined) and the name is a link to the journal. Look at some of the photos of the species represented keeping my suggestions in mind.
You can look at www.octopusid.com for a few hints and examples. Click on the opening blue screen and scroll on the left until you see Identifying Traits. It is a little difficult to navigate but the pictures may be helpful.
Then I am pretty sure you don't have a Pacific animal so keep the temps between 75 and 78. Now try to determine the arm length in terms of mantle:arm ratio. I suspect this is an Indonesian animal, probably in the Abdopus complex but arm length will help promote or demote that thought (however, the most common we see, aculeatus, will have purple/blueish sucker tips most of the time (all can show white so you have to watch for the tips to show color).
I kind of suspected that. Have a look at Espy to see if we are close. His name comes from Octopus SP, meaning an undetermined species. I think he was part of the Abdopus group but was not an aculeatus.
He spent most of his time inside the Live Rock and I suspect these are caught as LR hitch hikers.