Dr. Octopus - Young mercatoris

Icabod169

Cuttlefish
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Feb 21, 2009
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Hey guys,
My name is Alex and i just received a new young mercatoris "dwarf" octopus from Sea Life inc. His new home is a 7g desk tank that i decorated with live rock, old barnacles, a couple greek pillars, and some shaving brush plants. Although i know it might be bad, I added a couple tanksmates to the aquarium. There's a sure to be eaten green chromis (which helped the cycle process), a couple of nano pencil urchins, and a horseshoe crab that i made a separate sandy bottom for. The tank has 2 filters with foam guarding the intakes. I will keep everyone posted on recent developments!

Here are some pics i took while acclimating.
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sedna

Larger Pacific Striped Octopus
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Super cute little friend! I would encourage you to ditch the chromis, though!!! Fish that are aggressive enough to not get eaten are aggressive enough to damage your pus- most especially by biting at their eyes which can cause life threatening infections. I've seen chromis that were pretty docile, then again I've had some that would hold their own against triggers, even start the fight.

I'll wait to let others chime in about the urchins, and as you said the crab might be food but then again might be ignored by your octo.
 

DWhatley

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Alex,
The tank is likely to be OK for a few months but 7 gallons is too small for the life of the octo. I would recommend changing a gallon a day as part of your feeding routine even now.

Please take the chromis out and see if you can trade it for something useful (pair of plastic tweesers for feeding maybe). Be sure your octo has a place to hide where the fish can't peck at it but you should not have both in the tank at all. NO FISH in this sized tank with merc, NONE! The tank can't handle the wasted even if the fish does not get a hold of your dwarf.

The horseshoe is fine but will either die or out grow the tank quickly. A larger octo might try to eat it but I don't think there is an issue with the merc, certainly not at this size but check that it is alive EVERY day and don't let it stay dead in the tank overnight if it dies. At 7 gallons you have very little biologic (if any) filtration and water can go bad overnight.

The pencil urch should be fine but it will become a meat eater. They will eat plant (seaweed and algae) and a little meat naturally but become soley meat eaters - which includes some corals - if there is not enough algae and they don't seem to revert once they start so you will need to provide some dead shrimp or something similar and then be sure any remains are removed before the water quality is effected. I have used dried seaweed but it often has aptasia that will spread when hydrated and can start a problem.

I would encourage you to start a tank twice that size now so that it can be cycling.
 

Icabod169

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Thanks for the pointers! First of all I didn't know that chromis could be aggressive. I just thought he'd be a snack or something. I just got off work and took a look inside the tank. Doc has made a home inside the bottom section of the old barnacles and i gave him a shell to use ass a door. Hopefully I can get him to eat a minthrax tonight. I was also wondering if I could use a blue led instead of red to see him at night cause I had one of those lying around. I know the tank is kinda small but it was first cycled to house cuddlefish but the eggs never hatched :sad:
 

forever27

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A lot of times chromis aren't too aggressive towards other fish and inverts, but I'm sure the one you have is too big for your octo to eat. Therefore, as D and Sedna have already stated, it'll probably nip at or attack him/her. Especially in such a small aquarium. Be sure the crab is small enough for him to eat as well. I use a blue light to view my O. luteus at night, also a nocturnal species. Just make sure it stays pretty dim or he won't even bother coming out.
 

DWhatley

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The reason for using a red light is based upon studies that indicate octopues cannot see red. In theory, using the right frequency of red, you could have the tank fully lit and the octo would think it was dark (sometimes you will see zoos use this for bat houses and infrared light). I am not 100% sold on them not detecting the light (LED seems more detectable than red velum filtering but both seem to work well enough to be able to observe nocturnal octos). One of our New Zealand members (Dr. Jean, University of Otago, Portobello Aquarium) has noted problems with a large daytime octopus and blue lighting (like actinics) but none of the smaller animals have been reported as objecting. One of the things I do is to leave the red light on 24/7 so that there is no "darker" period. I have raised two generations of mercs (one group captive raised, the other captive bred) using this kind of lighting scheme without known problems (the oldest of each group lived over 12 months and the original wc lived 11 weeks post hatch). However, it does not mean that it provides any benefit :hmm:

The barnacles were a good choice for a den option. Several of my mercs have chosen them and I had much higher visibility than the ones (with the exception of Sisturus) that chose to live in the live rock.
 

Icabod169

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Doc just took his first feeding! I just lured a small thawed krill in the "Hinges" of his shell door and i saw a small shadow then something snatched the krill. I'll make sure tomorrow morning that he ate the whole thing. I put the blue led up until i get a red one but it's real dim and i dont think he will notice. I'm keeping my eyes open...:cyclops:
 

DWhatley

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As long as the horseshoe does not die, he will make a good scavenger. He cannot bite the octo (if you gently pick it up and place it in your hand you will see that it has no ability to bite :rolleyes:) and there is little chance of the telson doing any damage (it steers and rights itself with it). My concern is for the crab's survival in the tiny environment.
 

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