Still in planning stages


Pygmy Octopus
Mar 15, 2006
Hello, everyone. I'm just getting started on this long road, and had a number of tank-related questions to ask. When I say "a number" I mean a large number.

I'm thinking of using (probably building for myself) a 75-gallon acrylic tank. I definitely want to use an overflow box, but I don't know exactly what all is involved. it seems most of the sites I've found about them assume a fair level of knowledge that I simply don't have.

I've become probably overly paranoid about having small gaps and holes where my future octopus could get his arms caught and hurt. How big should the slots on my overflow box be? I don't want them big enough for him to get through, right? But how small is he going to be when I get him? Can I make the gaps too small for the thing to work? Is that even possible?

Also, what are the best methods for keeping the top closed off to curious beasts? Should I just put a layer of glass over it and weight it down? How much weight could an adult octopus lift in that situation? Should I put on a latch with a simple lock of some kind? How large of a hole in the top do i need to be able to feed and care for the octopus without making it too easy for him to escape?

Is there a wayto light the tank without getting it too hot and making my acrylic all melty? I know fluorescent lamps don't get nearly as hot as some others, but would it still be too hot?

I'm sorry for all of the questions, but I'm very new to this idea and very excited about it. i realize it will be quite some time before I get anywhere with it, but I want to start planning as soon as possible. Thanks in advance for your help, everyone.

TidePool Geek

O. vulgaris
Jul 18, 2005
Hi Septimus,

If you haven't already, read the ceph care articles elsewhere on this
site. They'll tell you just about all the general information you need
to know.

What they can't really give you is specifics relating to the species
and size of your particular animal. With the demise of Octopets, most
octopuses on the market are questionable as to species, life
expectancy, and, most importantly, husbandry requirements. The biggest
variable is temperature; for example, O. rubescens is best kept at 50F
(10C) while O. bimaculoides wants 60F (16C) and many of the truly
tropical species will be happiest at 80F (27C). Your best bet is to
avoid buying an octopus if you don't know what species it is. Failing
that, you absolutely need to know where it was collected if you want
to get the temp. right.

A couple of comments about ethics and safety: There are some species
on the market that probably shouldn't be. The so called Mimic octopus
and the Wunderpus are two species that are becoming popular because of
their attractive markings and/or unusual behavior. The thing is that
neither of these species (and the two are sometimes confused by
retailers) are very well understood and it simply isn't known if the
natural population can stand up to much collecting for the hobby
trade. Another questionable group are the blue ring species. These
little fellows are easily collected and very pretty but, they have a
reputation for not shipping very well and being very short lived in a
home aquarium. Added to that is the fact that they are very venomous
and it's possible to receive a fatal bite from one (confirmed
fatalities are rare but it still needs to be considered).

As to escape proofing and the safety of the octopus: Octos tend to be
very curious about their environment so any pumps or powerheads need
to be screened to prevent exploring arm tips from being pureed.
Fiberglass window screening is one fairly easy and economical
solution. Since an octopus can squeeze through any gap larger than its
beak, you'll need to make sure that there aren't any such gaps in your
system. What that converts to in terms of actual dimensions will
depend on the size of the animal but I'd be concerned about anything
over 1/8" (3mm). It's a fair assumption that an octopus can lift (out
of water) something less than its own weight but that's not the end of
the story. We've had GPO's escape from a tank with a very heavily
weighted top; what happens is that the animal finds a spot where the
top can be slightly bent such that there is a sufficient gap to get
through. My suggestion is to think in terms of either securing the top
all around its perimeter or using a material that doesn't flex such as
a fairly thick pane of glass.

Confineably yours,



Pygmy Octopus
Mar 15, 2006
I hadn't heard about that temperature requirement for Bimacs before. Do I need a chiller, then? My ambient room temperature is probably 68ºF most of the year. If I can find a Bimac, that's what I would prefer to get, for any number of reasons. Still, adding a $700 piece of equipment to get the water temperature optimal is pretty rough. What are my other options, or are there any others?


Staff member
Nov 20, 2002
Dallas Texas
Hi and welcome to :welcome:

Alex is correct about bimac temperature, but most of us have kept bimacs without chillers. They tolerate some variation in temperature, and if 68 degrees is your basic temperature, you should be OK. You can also lower the temperature several degrees by aiming a fan onto the sump. Pumps and lights may raise the temperature a bit.

I have an Oceanic Systems tank and it has what I would consider "standard" overflow holes. Yes, a small octo could get through, so I wove plastic mesh in and out of the holes to make it octo proof. As for the top, duct tape is your friend! I used duct tape to hold the lid down and replaced it frequently. You will need some venting in the top, too.

You won't need bright lights, you could use fluorescent. Lights are usually elevated a bit from the glass and that helps with heat.

It's good that you're starting to think about all these things early on - a good octo tank requires planning, not to mention the cycling time.



Pygmy Octopus
Mar 15, 2006
Is there any reason I need to keep the top of my overflow open? Could I put narrow slits in it (1/8" or so) and the put a cover over it, to keep the octopus out? It seems that the majority of the problems people have with these have come from having the open top (so snails and fish can get in) or the holes too large (allowing smaller things in). If I can negate these two factors, wouldn't that be better?


Jan 4, 2006
You need to keep the overflow open to be able to maintain the standpipes and access the bulkheads at the bottom.

What I did was have the overflow cover go all the way up to the glass top of the cage. This means that the slats are longer than normal and more more water can get in if I need it to, but the top is open for adjusting my Durso standpipes and bulkheads. That is one of the benefits of a custom tank like you are making, easier to make it octo proof.

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