[Octopus]: Hank the Bimac


O. vulgaris
Nov 18, 2019
San Bernardino
This is me and my boyfriend's second Bimac and won't be our last. As stated in our Tank Talk post we accidentally acquired our first one from a wholesaler who mislabeled it as a Pacific Dwarf octopus but neither of us had ever owned one or knew of anyone that had kept a cephalopod before so we were worried it may be of the venomous variety as we also didn't know there were more than one type of Blue Ring. Although we had done extensive research, well as extensive as the internet allows, we knew it was not a Pacific Dwarf after we saw it's blue eye rings appear but the animal did not display them right from the start so it was kind of a shock I guess but we narrowed the type down based on searching key terms and verified with an aquarium service business, in San Francisco, where we were living at the time who actually wrote an article on cephalopod keeping, Daniel Pon. We must of had him/her for about 6 months before sadly passing away. Which is something we anticipated since it was a fairly large sized animal who was most likely at the end of it's life cycle. Ever since then we had been looking to home another but we knew the odds of getting another Bimaculoides, short of acquiring a permit and catching one ourselves, wasn't going to happen. We pondered the idea of going out and potentially "rehoming" one since it seems these days captivity is becoming more beneficial due to the conditions the oceans are becoming but we both come to the realization that it seems there is so much taken, and not just from the oceans. We felt that with all there is being taken for "our" benefit it seems nothing is ever given back or if any,very little is given back to benefit the other inhabitants. I didn't want this to go into a rant but back when we lived in the Bay Area and would go walk on the beach it was so trashy and people would take their dogs and tie up their animal's waste and leave it. There were many times I would pick up things that I could to properly dispose of it in the trash. At one point I got so fed up with seeing it that I wanted to start bringing trash bags to pick up all that we saw but it wasn't practical as there was just so much that one bag wasn't gonna due and the trail down literally takes your breath away so trying to haul up a bag full would seem impossible. So ultimately we stopped going to the beach and decided to not go that route and we decided to look for another species and were okay with not seeing all the time like the Bimac. Anyway sorry for my slow intro but I wanted to give some insight into our journey with this amazing animal.

As the title suggests we decided to name our octopus Hank, like the one from Finding Dory. I had been familiar with this forum group from before during my research into owning octopus but I had not established an account since I have not had very good experiences with public thread sites but after seeing there was a potential at getting another Bimac I didn't hesitate. We currently have his tank at 1.026 salinity, 8.2 pH, and set at 70°. (A special thanks to Tonmo member pkilian for suggesting a temperature range of 60° -70°.) We have used an RO/DI system to mix our water and use the Red Sea Coral Pro salt mix. However after the tank cycling completion we had a brown algae outbreak begin so we added a small cleanup crew. 10 small hermit crabs and one Sand Conch that have been doing a good job keeping the algae at bay but have increased the nitrate level slightly but that is to be expected. When we pulled him out of the box we checked to make sure he didn't ink during transportation and then after observing he/she hadn't we floated the bag for 30 minutes to adjust the water temperature to match the tank before we started the slow drip acclimation for 3 hours. We have done acclimation for as long as up to 4 hours to make sure the animal is fully adjusted as we are in no rush and better safe than sorry as you can't really say sorry after an animal is dead. We have been trying to identify if Hank is a male or female but as long as he/she is healthy we don't really care. Ideally I would like to be able to tank raise octopus babies to help cut down on the capturing of wild specimens but I have a lot to learn before then. I apologize for jumping around but my mind is random at times and rarely stays on point but I have been trying to focus my thoughts more. Last night I was simply intrigued just seeing the pupils dilate with light fluctuations. It never occurred to me that their eyes are like ours, I just thought it was cool to see them adjust to the light or lack thereof.

After going into the tank after we felt comfortable with his acclimation, he/she did not explore much. We wondered about him potentially going after our cleanup crew but we figured since they were in there first he may not go after them right away and from what we have seen he hasn't bothered them yet. He found a corner with a rock he/she was comfortable with and began digging or I guess trying to dig a den. He has now found the caves and hollowed out areas of the live rock I had made for him so we have yet to see him but know he's in there as we see sand "dust" bellowing out him digging inside so I'm glad he's getting more comfortable with his surroundings. I have attached some pics of him floating and in the acclimation bin, and some clips of him digging. We purchased some live bait buckets by Frabill that work really good for fish they have a built in aeration system and a foam insulation layer. We purchased them for when we moved from Texas to San Francisco, back before we had a saltwater tank. They work well for short periods of housing both freshwater and saltwater fish but sadly we lost all of our saltwater babies when we moved from San Francisco to San Bernardino because we had like a week gap before we were able to get our tanks setup. We were relocated through my boyfriend's work and we didn't expect it to take that long even after stressing the delivery time urgency for the sake of our animals. We had a young banded cat shark that we raised from an egg pouch and got to see him grow from inside, a blue spotted stingray, a blue and black ribbon eel, some green chromis and blue damsels that all coexisted peacefully together and sadly passed together during our wait. We were both frustrated and heart broken. It was a hard lesson to learn and it was out of our control which was the hardest part. After talking we decided to try for another octopus and the timing just happened to be favorable as when I got on Tonmo to look and saw the post that there were Bimacs that were going to be available and the rest is history.



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What a great looking octo! You may already know this, but one way you can sex out your bimac is to look for the presence of the hectocotylus (it's the third arm from the right if you are counting clockwise around the animal). Males have one and females don't. The arm tip will look slightly different, and have a small groove running down the middle of the last few cm of the arm. I'm sure you can find photos of this online.

Heres hoping you have a female and she gets comfortable enough to lay some eggs! If you do find eggs in her den, please make a post! I have lots of experience and suggestions for raising bimac babies. They can be fussy but with the right steps and housing you can have lots of little octos running around.
Good Morning Everyone,

Here's a little clip of Hank peeping out of his cave entrance displaying a very cool striped or marbled patterning. I have noticed this one is more skittish than the one I had prior but I'm hoping he'll warm up. We gave him a live fiddler yesterday which I just pulled out what was left of the crustacean but he didn't immediately go for it like the one from before. He has not touched the clean up crew that's still working away on the algae you can kind of see growing on the cave entrance. So all of this,so far,from the color to the demeanor has all been new territory for us. Our first one was a very aggressive eater/tank mate so anything he could catch and eat he would.
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Great vid!! I was watching with my wife, she asked, "chilling, or adjusting"? I said, it seems like he's more chilling than adjusting! :-D Thanks for sharing!
Hey, how did Hank handle the holidays? Hope everything remains well!
Hank is doing well. She is really feisty. An aggressive eater and she tried to bite my boyfriend but we just can't get enough of her personality. We sometimes catch her at the top of her tank watching tv or seeming to be looking at what's going on above her cave/lair.
Hank has started laying eggs. She has been reclusive this last month, won't come out to eat but sticks and arm out to grab fiddlers. We figured that she was probably gonna lay and we see the first one. I'm only able to see one egg so far and have taken a couple pics and a small video. Unfortunately it is also an indication she is in the last cycle of her life. We were really blessed to be able to care for her and to be a part of this group otherwise we wouldn't even have found her. We'll keep everyone updated on if there's hatchlings. It's ironic because we were trying to get baby Caribbean Reef babies with Turq, since they are fully developed mini octos when they emerge, but it just didn't pan out with him getting caught in a wave pump.


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You won't see anything for several weeks, however, since you have had her for over 3 months, it is very unlikely that the eggs (unlikely there will only be one, the rest are likely deeper into the cave) will be fertile.
You won't see anything for several weeks, however, since you have had her for over 3 months, it is very unlikely that the eggs (unlikely there will only be one, the rest are likely deeper into the cave) will be fertile.

Even if she mated before capture and held on to the sperm? She was fairly big when we got her. The cave is really small and she blocks it most of the time but I still only see one and I would think they’d be clustered together. I was looking yesterday and couldn’t see it anymore. I don’t know if they can move them or would move them but she doesn’t come out ever.
You won't see anything for several weeks, however, since you have had her for over 3 months, it is very unlikely that the eggs (unlikely there will only be one, the rest are likely deeper into the cave) will be fertile.
“The male octopus has a modified arm called the hectocotylus, which is about 3 feet (1 meter) long and holds rows of sperm. Depending on the species, he will either approach a receptive female and insert the arm into her oviduct or take off the arm and give it to her to store in her mantle for later. In the latter scenario, the female keeps the arm until she lays her eggs, at which time she takes the arm out and spreads the sperm over her eggs to fertilize them.” As you stated it’s most likely not the case but possible I guess?
There are not too many (only one I know of) male octo species that actually give up their arms. Some, however, do give up their lives if the female is particularly hungry, ornery or just in a bad mood (we really don't know why some males are cannibalized and others of the same species are not). Yes, the female stores the sperm in both cases but the expected viability of the sperm is only about 3 (4 at the most) months.

If she is guarding the cave there is likely a larger clutch inside. You might try taking a video and then enlarging it to see if the camera can pickup more than your eyes (I have often found this to be helpful).
Your first sign of viability on the eggs will be black dots in the eggs so it will be helpful to try to take photos every few days if you can get an angle that shows an egg. These will be the beginnings of eyes.

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