What species would be best for me?

Tatumj96

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#1
I had thoroughly researched O. Mercatoris here on this site several years ago and was about ready to set everything up for a specially made micro-reef LLC setup when I learned that the college dorm I was about to move into would not allow even fish tanks, so I set the idea aside for awhile. Now that I have graduated, I've started a saltwater tank and am thinking about a cephalopod again. I have a 48" long, 18" deep, and 13" high tank that has been up and running for about a year. It doesn't have much in it at the moment: 2 clownfish, 2 damsels, a royal gramma, a lawnmower blenny, a banded coral shrimp, some snails and hermits, and some zoanthids. I have an overflow to a sump and could easily secure some netting or a top over the main tank. Most of my live rock is in the sump, along with chaeto, carbon, heater, and protein skimmer. I keep the temperature between 78F and 80F degrees. There isn't much space taken up on the 1" thick sandbed, I have one rock near each end of the tank that are maybe 5"x5"x5", and then a large bonsai type of artificial coral with shelves that takes up maybe a 12"x5" area of floor space in the middle of the tank. Moving these around would be fine as well if having them grouped instead of spread out would be better for swimming space.

I have several questions:
1. Would I need to worry about an octopus working it's way through the return hose coming from the pump inside my sump? I think it has an inner diameter of 3/4" or 1".
2. What would be the best way to prevent an octopus from getting inside the overflow box and entering the sump?
3. While most of my parameters are good, my pH is only at 7.8. It stays there continuously, no matter how much buffer I dose. I do use an RO/DI unit, but have been told since I live in an old house currently with no HVAC system it is likely due to high ambient CO2 level in the house. Is this pH just too low?
4. I do sometimes dose carbon in the form of vinegar between water changes just to make sure my nitrates stay extra low. Would this be a problem? Should I stop doing that with an octopus?
5. And finally, what species would you guys recommend? I understand with a tank this size that I am limited to one of the smaller species with a shorter lifespan, so a large egged species that would be easy to breed would be ideal, unless there is a longer living species that would do well in a tank this size that I do not know about. And if I get a short-lived species that I will need to breed, I would like to keep two or three of them to try to ensure breeding instead of hoping I get a pregnant female. A species that would leave my fish alone would be nice, but since none of them are bigger than 2" or 3" I anticipate having to move them. If I have to move the fish anyway, then changing the temperature of the tank for a colder water species wouldn't be a problem.

Thanks in advance for any and all help,
-Josh
 

Tatumj96

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#2
I still need help with questions 1-4, but I think I have decided for number 5. My 3 most enticing options were mercatoris, hummelincki, and bimac. A bimac would require colder temps than I currently run my tank and I would need a chiller, and since I am on the east coast it would have to make quite a trip. A hummelincki is tempting, but the reported frequent inking is steering me away from them. So I think I have decided on my original intention from when I first thought about keeping an octopus: O. Mercatoris.

I would probably leave the 2 clownfish, lawnmower Blenny, banded coral shrimp, and zoanthids in the tank. The clownfish are very peaceful and will likely leave an octopus alone, and hopefully avoid becoming a meal at least for awhile. The lawnmower Blenny is quick, I think he would be tough to catch. I doubt the banded coral shrimp will last long, I might move him too but haven't quite decided. The yellowtailed blue damsels are very quick, but I know damsels are known to Peck at the eyes so I will remove them. The royal gramma is my girlfriend's, so I am not risking it becoming a snack.

So I am thinking a pair of mercatoris octopi. Gulf live rock says to contact them for availability on mated pairs, hopefully that is something that they can do seeing as they talk about it on their website. Does this seem reasonable to you guys? I would love to hear any and all feedback, and especially any answers on my other questions!
 

DWhatley

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#3
#5 Starting with "choosing" a species and tankmates. Have a (re)look at my infamous rant on species selection and make sure you accept that 90% of the selling facilities have no clue as to what octopus they have to sell, especially if they acquire their animals from a wholesaler (who 99.9% have no species clue and rely on the labeling that is always generic). There are a few (those that do their own collecting) that know the animals in their local waters and will ask a trusted source :evilgrin: if they are not sure.

There is no such thing as a "mated" pair when it comes to octopuses. They are not monogamous and most vendors don't know enough to be able to tell a male from a female (in fact, visually we can only spot sexually mature males and the absence of a curled third arm only suggests the animal is female). There is a hope that perhaps these animals were found together and have not killed each other while living in a tank. There are only a few species that we have seen successfully housed together (most are cannibalistic) but even with O. mercatoris (the only common species like this) need to have been found together or at least be of the same size. Fortunately, mercs are often by catch of live rock collection and are siblings or at least used to living in close proximity. Finding a merc, however, will be a challenge as we have not seen many for quite some time. Their lifespan ranges from 8 to 12 months and we have had some success with a few generations grown in captivity.

There are only a few long lived octopus species (4-6 years) and all are far too large for a home aquarium (some are pelagic and not kept even in public aquariums). Cold water animals do tend to live slower, longer lives and we have journals of bimaculoides living almost 3 years when kept at temperatures below 65. A bimac can survive in 72ish waters but its lifespan will be more like a warm water species of about 1.5 years. O. vulgaris is also longer lived in cold water but our east coast animals have an estimated span of about 18 months.

If you have read any of my suggestions for new keepers, you will notice that I am an opponent of ANY fish in an octopus tank. Octopus and squid are the true "chicken of the sea" and a nice ball of protein for anything that is hungry for meat, anything else is prey. Even peaceful fish will pester them for food scraps if they don't outright attack, inducing additional shyness or aggression. An octo produces far more waste than an equivalently sized fish so adding more waste producers also adds water contaminants. Here is a nice discussion about what has and has not been documented as successful tankmates.

#1&2 I believe you have a weir around your overflow. There are a couple of solutions for keeping octos out (yes, they will find their way to the sump if not restricted). If the animal is small (young or a dwarf) then very coarse sponge (the rougher the better) in the weir works well. I recently found this at Home Depot that looks like it may work well but I have not tried it to see how well it allows water to flow. I use something similar but it is a bit more porous. The other thing I do on one tank is to place a white light over the weir so that it is alway well lighted. It won't keep curious arms away but does dissuade nocturnals from seeking a nice dark place to hide. Lastly, and I recommend this along with one or both of the other suggestions, you can buy a strainer that will fit into your bulkhead. You will need to determine the size of your bulkhead AND if it is threaded. If the inside is smooth, you will need the "slip" fitting.

#3&4 You MUST raise your PH to 8.2-8.4 (the higher preferred). Try adding an air stone to your sump (NOT the display) and stop adding the vinegar (vinegar is acid with a PH of about 2.5 so, yes you are lowering your PH every time you douse it). Until you move your fish, you will want to raise this slowly by adding the air stone, not using the vinegar and only doing regular water changes. A rapid change will kill your acclimated fish, an octopus will not acclimate. If you move the fish, then I would suggest major water changes and adding buffer to your saltwater until you stabilize.
 

Tatumj96

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#4
Hmm an octopus may not be possible at this time then. The pH will be the big problem. I have always had an airstone in the sump, as well as powerheads causing surface turbulence in the display. Even before I started dosing vinegar the pH was always about 7.8, even when adding buffer. Maybe I will try several more test kits or get water sent out for testing, I guess there is a possibility that my test kit is just old or off a bit, because pH has always been stable.

If I can get that corrected, I was thinking some fine netting over the tube intakes inside the weird and the pipe coming back from the sump. And I can remove those fish then, I forgot to mention that there is a porcelain crab in there as well but I have tried to catch him before which is impossible, so I guess he will stay.

Okay, so I guess the mated pair thing is a bust. Have you heard anything about the type of species received from gulf live rock? In the inverts section on their website they say they can get o. Mercatoris, and the picture example looks like one to my untrained eye. I guess I will ask for one unless they happen to have two come in on live rock together.
 

DWhatley

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#5
I took a look at the website (I don't know anything about them), Their about page fits with where most mercs would typically be harvested, more as by catch found in the live rock after collection than intentional collection. There are collectors who have kept octopuses and have more knowledge than most retailers but octo knowledge is pretty scarce, even for basic sexing.

Please do try again for the little porcelain crab as she won't make it 24 hours if you have to leave her in the tank.

I meant to suggest picking up new testing chemicals (or strips. I particularly like having strips for acclimation and find reagents to expire before I use them up). Do bring water into your local pet store on your next visit for testing but be sure to take it from the tank just before you leave.

Another thing you might look at is replacing your sand with a neutralizing substrate like Argonite. Also, test your fresh water and your mixed saltwater before you top off or water change to see if the problem is at the water source or after it is n the tank.
 

Tatumj96

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#6
I took a look at the website (I don't know anything about them), Their about page fits with where most mercs would typically be harvested, more as by catch found in the live rock after collection than intentional collection. There are collectors who have kept octopuses and have more knowledge than most retailers but octo knowledge is pretty scarce, even for basic sexing.

Please do try again for the little porcelain crab as she won't make it 24 hours if you have to leave her in the tank.

I meant to suggest picking up new testing chemicals (or strips. I particularly like having strips for acclimation and find reagents to expire before I use them up). Do bring water into your local pet store on your next visit for testing but be sure to take it from the tank just before you leave.

Another thing you might look at is replacing your sand with a neutralizing substrate like Argonite. Also, test your fresh water and your mixed saltwater before you top off or water change to see if the problem is at the water source or after it is n the tank.
Do you have any specific test strip brand recommendations? I use the API Marine master saltwater test kit now. If I get far enough to even think about purchasing an octopus I will just take the rock the crab calls home from the tank and replace it with another, he recedes in it any time I try to get him and becomes unreachable. Could I just dump crushed aragonite in my sump? I like the sand in the display, and I have a whole bag of aragonite gravel already actually.
 

DWhatley

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#7
My only problem with putting any substrate in the sump is keeping it stirred and clean. This might not be a big issue if you filter your water as it dumps to the sump (I dump my display into a filter sock containing carbon so very little trash gets into the sump). If this is not a concern, sure, argonite, LR and macro algae are all popular for sumps to help with water quality.
 

Tatumj96

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#8
Yeah I have an overflow box where debris is filtered out before the water is pumped to the sump, and then I have live rock and ceramic cubes made to act as live rock in the sump itself. I added a section of aragonite in there. I needed to clean my chaeto in there tonight anyway.
 

Tatumj96

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#10
Here is a cute video of an octopus with a diver. Fun to watch but what I wanted to point out was how the octopus reacts to the fish (and visa versa)

That was very cute! I definitely see what you mean about the fish, wouldn't want to stress the fish or the octopus if I can help it. Plus, moving them will save me a potential loss and I think just be an ethically better decision overall. Thanks for the video!

After adding the coral the pH does seem to be a little higher, I'll give it a couple days then get some test strips as well as see if I need to try adding pH buffer.
 

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