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Would this work?


Jan 20, 2003
It is my main goal to keep a healthy octopus in my 75 gal. tank. My parents are not too keen on the idea, as they really like the colorful fish. The tank will be in our den area, so many people will see it. I was wondering if it would be possible to put a divider in the middle of the tank so that the octopus was on one side, and the fish were on the other. I would make sure that there was no possible way for the octopus to get over to the other side and eat the fish. Is there anything else that must be done? My trickle filter is rated for aquariums of up to 150 gallons. I have found it a good idea to use things that are rated higher than what you're actually using them for. But you guys already know that. Any help would be greatly appreciated.

Yeah it does work and I have a similar set up at present for one octopus. It invloved me drilling the partition at water level and the water flows from the fish side to the octo side and into a filter then back into the fish side.

The skimmer is in the fish side as that posed an escape root.

The hole is sealed with a fine mesh siliconed in place.

It can be tricky to make it escape proof and I used a lot of glass and silicone, made easier by the fact i used to work for an aquarium building company :smile: but it can be done.

How about if you set two tanks up on a stand that allowed them to be filtered by the same pump. Set up a tank underneath like a sump and use that for the octopus... Ive done that too.

I would do the two tank deal, but my 75 gal. is gonna be in the wall. I'm glad that this will work. They sell tank dividers that have the small holes pre-drilled, would these provide adequate flow through the tank. Should I have my overflow on the fish side, and the return tube from the pump on the octopus side, or the other way around? Would this allow for the water to flow through the divider? I also might just make my own out of acrylic. My final question is about lighting. What are you currently doing with the lighting? I'm kind of stumped as to what to do regarding lighting.
Hi wee Matt

Well for lighting i am currently using a 30" tube that is high in the red spectrum (30watts i think, cant look at it right now) An dthat is on a timer for ~7 hrs a day

I think that you should have a small internal filter in the octo side to help with the excess waste from it and keep all other equipment like teh skimmer in the fish side. remember that a ceph acan produce three times as much waste as a fish of a similar mass so that cuts your stocking density right down!

Make sure that the octo cant put its arms through and grab fish, cuz it will given the chance... Lastly making a DIY split tank will be a real project for making it escape proof! :shock:

I think I'm just going to buy a piece of acrylic and some silicone and go to work. I don't think I should be too tough, as the tank isn't set up yet. The only thing I could think of is if the octopus breaks the netting. Other than that I have no worries, as I work with my hands alot.

If I make sure that the overflow is meshed up, can I place that on the octopus side and the return on the other? Or would this cause a problem because the return is on the other side and maybe he won't get enough oxygen?

Colin, do you think you could post a pic of the current set up you have now? Im interested to see what it looks like and I would like to build from that. Thanks for the help thus far.
Hi Matt.....

I ocasionally get to use the camera my gf uses for work so if she brings it home in the next couple of days I'll be sure to post a pic or two for you, and of my new octopus.

With my tank the pump is on the octo side and goes into the fishtank side then flows back into the octopus. So that works for me and i also have a rena 400 supplying plenty air in the octo tank.

that help?

Colin, thanks for the help. Is that all you have for filtration, or do you have an internal filter on the octopus side as well? I think I'm all set on what I need to do, my main thing was just checking to see if it were possible. Thanks for the help.
Hopefully 'M' (my girlfriend) will bring home the digital camera today so should have it for some tank pics this weekend!

The tank has quite a lot of LR and an aquamedic 1000 multi skimmer and a fluval 3..... thats it, dead easy!

Not trying to steal your thread Matt, but I've been trying to plan out an Octo-Aquarium myself and I want to know what everyone thinks of this. What if I took an aquarium(30 gallons or larger) and used drilled plexiglass or some other divider to section off the aquarium(this would be siliconed in place). Sectioning off about 12 inches on one side to hold the skimmer and filter and keeping the octopus on the other side. That way I could silicon the top down(except for a locking door) on the octo side and there would be no escape routes. I guess it would be like a small sump built into the tank. If this would work, should I drill a lot of holes through the divider, or just at surface level. Also, if I had the filter on the sump side, should I extend the intake or out flow to the octopus side? Would anything else need to be on the octopus side like an aireator? Thanks in advance, John
Hi John
have you thought about using a sump? That is a lot easier to prepare and make octopus proof... Most LFSs can drill tanks themselves and it can make your life much easier... the sump doesnt even need to be all that big.. just 5 gal or so... enough to hold your equipment and the overflow if the pump stops.

You would still need to add lots of surface movement to the octopus as it has high needs on oxygen.

I have found that when building an octopus tank that by siliconing glass round teh top of the tank to create a 2 - 3" overhand that certainly smaller specimens cant seem to get round it, so your door idea would work

My main problem with the sump was that I thought I would have to buy an expensive pre-drilled aquarium to use one. When you're talking about my LFS drilling my aquarium, do you mean a plexiglass or glass aquarium? Because I am planning on using a glass aquarium and I didn't know they could drill those. Thanks for the advice, John

I think the LFSs at one time did drill aquariums, glass and acrylic. However, I called around and was told that only manufacturers did this now. So this may be a difference between the US and Scotland, or you may be able to find a small LFS that still does it, but it's not that common.


it is perfectly normal to asume that a glazier will drill the tank for you, it is actually very easy and over here costs about £5 per hole. I would phone up a few local glaziers and they should do it for you... maybe get them to practice on a spare bit of glass first LOL

On a safety note, i have read that many USA tanks have toughened glass bases which will be marked by a toughened stamp... if you try to drill that it will explode!

Drilling tanks is relatively easy, all my tanks are drilled and even one that was full of water at the time!


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