Hi there!

[jcross]

Hello all!

I haven't been lurking for very long, but I found the forum because my LFS recently got in two "Pygmy Octopus" and I'm strongly considering picking them up once I modify my IM Nuvo 20 to be octo-proof. That being said, while I'm told they could be mercatoris or joubini, I'm not sure which as I haven't gained an eye for identification just yet. I've kept (and still keep) reefs, FOWLR, planted tanks, and tropical vivariums and have been doing lots of reading on care for both species, I just wanted to get an opinion on what species they might be and any general care tips anyone may have. Thanks!

Pictures (I know it's just the underside, but it wasn't me who took the pics, I will try to ask for pics of the head & eyes as I know those are defining features):

 

[tonmo]

Welcome to TONMO, thanks for joining! Is the Nuvo 20 a 20-gallon tank? Might be a bit small, even for a pygmy -- our experts can weigh in on this. I also understand LFS can often get the species wrong, so there's that to consider... How long has your tank been cycling, and can you share its parameters?

 

[jcross]

Yes! It's a 20 gallon! From my reading on the forums and elsewhere, joubini and mercatoris should be kept in a bare minimum of 10 gallons but are comfortable in 20-30. Tank's fully cycled. 1.025 salinity, 78F, 0 NH4, 0 NO2, 5ppm NO3. I've set up a refugium and protein skimmer in the back to keep nutrients to a minimum. Lots of live rock, a 1.5in sand bed, minimal light with red light at night. I also 3D printed two giant barnacles for them and have actual giant barnacles being shipped right now.

That being said, we are looking at getting a custom tank made soon to move them into, so if anyone has any suggestions on going bigger or what dimensions are recommended, I'd love to know.

 

[tonmo]

cool! While we wait for insights, here's a classic thread you may find useful:

Dwarf Octopus Tank

Hey everyone, new here and very glad there is a forum specifically for cephalopods and octopus. I've been doing some reading the past few weeks about dwarf octopus since I saw one at my lfs recently. My setup - 10 gallon DT tank, 5.5 gallon sump with Refugium. Currently a reef with several...

tonmo.com

 

[jcross]

cool! While we wait for insights, here's a classic thread you may find useful:

Dwarf Octopus Tank

Hey everyone, new here and very glad there is a forum specifically for cephalopods and octopus. I've been doing some reading the past few weeks about dwarf octopus since I saw one at my lfs recently. My setup - 10 gallon DT tank, 5.5 gallon sump with Refugium. Currently a reef with several...

tonmo.com

Thank you!

 

[pkilian]

20 gallons would probably work but if you are planning on making a custom tank I would recommend going to 30-40 gallons depending on the space you have in your room. How are you planning on making the tank? Are you building it yourself?

 

[DWhatley]

I've successfully housed a pair of mercatoris siblings in a 15 but also kept 3 in a 45 (also siblings) so you are good with sizing (here is a post I made comparing the two tanks). I can't help on ID from the images but one of the main visual differences between O. mercatoris and O. joubini will be arm length. O. mercatoris arms won't typically be more than 4 inches where O. joubini should be around 6. We really have not seen many O. joubini though. Most that have been named that are actually O. mercatoris.

Giant barnacle shells (never tried artificial) are great homes for the mercs and they take to them readily (especially the females). Most of the other species I have kept have preferred dens with a "front" and "back" door but the mercs have always preferred a single entrance.

 

[jcross]

20 gallons would probably work but if you are planning on making a custom tank I would recommend going to 30-40 gallons depending on the space you have in your room. How are you planning on making the tank? Are you building it yourself?

I know someone who makes custom acrylic tanks for a living, so I'm going to get it built and octo-proofed by him. Thanks for the size suggestion!

 

[jcross]

I've successfully housed a pair of mercatoris siblings in a 15 but also kept 3 in a 45 (also siblings) so you are good with sizing (here is a post I made comparing the two tanks). I can't help on ID from the images but one of the main visual differences between O. mercatoris and O. joubini will be arm length. O. mercatoris arms won't typically be more than 4 inches where O. joubini should be around 6. We really have not seen many O. joubini though. Most that have been named that are actually O. mercatoris.

Giant barnacle shells (never tried artificial) are great homes for the mercs and they take to them readily (especially the females). Most of the other species I have kept have preferred dens with a "front" and "back" door but the mercs have always preferred a single entrance.

Thank you for the insight! After more research and taking a closer look at them online, I'm fairly sure that they are mercatoris, especially since I've heard from multiple sources (including you) that joubini are hard to come by.