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[Featured]: Octoproofing glass tanks


Blue Ring
Jul 12, 2019
Hello all!

Below is an image of an aquarium facility where I'll be carrying out octopus research. I'll be using 12 tanks, each with a mother octopus that will have hatchlings of 4-5mm size.


To improve the tanks:
1) I'm looking for ideas of locking devices on the lids on top of adding bricks, since octopuses can be strong enough to lift even weighted lids (also a good idea to prevent anyone from tampering with the octopus if it's a key system or something) I thought of window stoppers but it seems that they require drilling for installation, like what I found here. Does anyone have better suggestions?

2) To separate in-tank devices from the octopus, I'll be ordering some customised perforated plates that look sth like this below. Companies I contacted could only drill holes of 2mm sizes minimum, so I'm thinking of sticking mesh nets on top of it on both sides - what do you think of fly screens or those eco mesh bags in terms of suitable materials (fibreglass, polyethylene?), and ease of tearing by hatchlings?

3) I've the same question regarding mesh but for the outflow pipes that you can see sticking out of the tanks to the floor.

Thank you!!
Hi Qiaz! It's nice to see that you are still making progress on this project.

I'm not sure how successfully you will be able to "lock" a glass tank, especially if you are unable to drill holes in the tank. Is the lab space you have not very secure? Is the chance of someone messing with your experiment a high probability? I might not understand the specifics of the space you are in.

One thing you could try in order to secure the lids more firmly, would be to have a velcro strap running over the top of the tank with attachments on either side of the tank, this would prevent the animal from sliding the lid horizontally. If you have enough weight on the lid (~7-10 lbs) you shouldn't have to worry about the octopus lifting the lid upwards, but they will still have enough power to slide the lid to the side, so that's what you should focus on trying to prevent.

I wouldn't worry too much about the hatchlings tearing the screen material. Also, I have used plastic screening in my tanks before and it didn't cause any health issues. I can try and find the specific brand I used in the past but as long as your mesh size is small enough the screen should work perfectly for what you are planning. Additionally, if you are using a mesh in addition to a perforated plate, you can probably have the holes in your plate larger than the diagram shows. With the setup as it is I would worry you may not get enough flow through the perforated plate. The mesh alone will be enough to prevent the hatchlings from escaping, so in theory you don't even need the plate, but it will be good to secure the mesh to something solid. (I would glue the mesh to the plate using coral frag glue, I can link the specific brand I use if you would like, but any should work just fine and cause no issues for the cephs).

For the drains, I would glue the mesh directly to the drain screen if that is allowed. If not, then mesh bags should be suitable as long as they are securely attached to the drain tube with a zip tie or something. What I would use is an aquarium media bag (I can provide a link if you would like). The mesh size should be small enough to prevent hatchlings from escaping. The bags may need to be removed every week or two to be cleaned to prevent the tank from over flowing. You will have to keep an eye on the tanks water levels to make sure you clean the drain screens before the tanks overflow, because the mesh will get dirty and the tank will overfill.

This is an exciting project! Feel free to ask any follow-up or clarifying questions if you have any.
Peter to the rescue again! :biggrin2:

Yes it's a very long planning process haha. Preventing people from accessing the octopus is a bonus but I haven't worked in that facility so I won't know until things happen I guess! The lids from memory do sit on a groove along the tank i.e. it doesn't slide by itself. So maybe velcro + bricks will do the job, thank you!

I was exactly wondering if the holes were too small to allow proper flow, glad that you pointed it out! Yes I was also thinking if it's sufficient to paste a bug mesh screen (link - advertised to prevent small insects) along the walls of the tank and forgo the plate.

I found this glue product - do you reckon this is OK? I've not used one before, does this work while gluing things in the water, or does the object have to be glued outside of water and dried before putting it back in water?

I also found this mesh bag online - what do you think? What's the best way to clean these bags? Are there other precautionary measures I can take when changing the media bag in the presence of possibly hundreds of hatchlings?
That mesh screen seems like it would be fine to use. From what I can tell, fiberglass is relatively safe for marine life, much better than a metal screen for sure. The glue looks good to use as well. If it is anything like the other coral glues I have used in the past, it should be okay to use under water, but it cures really quickly (think like 10-15 seconds) so you will have to work fast. Also, I would make sure to let the tanks cycle for a bit after you are done gluing. These are flow-through systems and not recirculating right?

The mesh bag seems like it will be okay to use. If you have the time it could be worth it to buy one as a trial and just make sure that the mesh size is large enough to allow the tank to drain properly. I think your best bet for the mesh bags would be to have one set of dirty ones, and another of clean ones, and then you can swap out a dirty mesh bag with a clean replacement immediately, and then you (hopefully) wouldn't have to worry about losing any hatchlings down the drain. I think the best way to clean the mesh will probably to be to scrub it with a dish brush and/or bleach the mesh. Do you have access to sodium thiosulfate to neutralize the bleach afterward?

Finally, can you remind me what species you are working with again? I have tried co-housing certain species of octopus in the past and their babies usually end up eating each other- they typically don't play well with others. Would this be a potential issue for you? It might be worth thinking of a way to keep the hatchlings separate from each other if necessary for your research.
@tonmo wow that's awesome thanks! Once I get some more logistics done, it should start in June or July! *stressed*

I went to check the hole size of the mesh screen and it's 1mm. The hatchlings will be 4-5mm - does this mean there's a good chance they can escape through it? Even if I get 100micron mesh, there's still the issue of it becoming dirty over time. Yes these are flow-through systems.

I'll be able to order some sodium thiosulfate either in pure anhydrous form or by solution, how many molar do you normally use and is there a particular procedure to follow?

I'm working on the southern keeled octopus (O. berrima) which has hardly been studied. Hatchlings would normally adopt a benthic lifestyle almost immediately upon hatching, although it's not fully studied/established. And yes that's one of the most important questions I wanted to ask - is it even possible to prevent cannibalism?

Also for nocturnal species like berrima, do you reckon it'd be okay for me to use a red head torch to observe them at night? Is it true that LED should not be used? The light for the aquarium room is fluorescent I think.
The hatchlings might be able to escape through the 1mm holes, but its hard to know for certain. It's probably better to be safe than sorry, so I would recommend having a mesh as a backup just to make sure they don't escape, then you can have your holes in the plate be a bit larger to allow for more flow through the tank, while not having to worry as much about the animals escaping. How will the dividers be secured in the tank? Will they be removable for cleaning?

To neutralize chlorine from bleach with sodium thiosulfate, you will want to use about 4-5 parts sodium thio to 1 part chlorine. Here is what Syndel's website recommends:
A range of approximately 2 to 7 parts sodium thiosulfate to neutralize one part chlorine is generally suggested, for example: to neutralize 1 liter of a 200 ppm chlorine solution, approximately 0.4 – 1.4 grams of sodium thiosulfate would be required, or to neutralize one gallon of a 200 ppm chlorine solution, approximately 1.5 – 5.3 grams would be required.
As you can see there is a very wide range that will be acceptable. I tend to go a bit on the higher end and then make sure to really soak and rinse my equipment in DI or RO water thoroughly afterwards.

One way you can try and prevent the hatchlings from eating each other would be to keep them separated in a modified bead organizer. If you drill out the bottom of each compartment and glue a piece of screen over the bottom of the organizer, you can allow for flow through the compartments. You might need to fuss with the lid to make sure it is secure enough to prevent the animals from climbing between compartments (using rubber gasket material or something), but I have used these in the past to keep all the hatchlings separated from each other. It is a bit fussy to clean and feed each individual compartment, especially if you will have a lot of hatchlings. Maybe experiment with a clutch or two to see if they will cannibalize each other or not before going through the trouble of setting up the whole bead organizer system.

I think a red LED should be just fine for brief viewings during the night. If you have the budget you could also get an IR flashlight and an IR headset or camera to be able to see the animals without using visible light.
Hello Peter!

Apologies for the late reply. I visited the facility and it turns out that I can't permanently fix anything to the tanks or modify them i.e. no glue, no velcro, no glued dividers etc. Their tanks are also sadly not well-maintained in terms of having lots of salt residues, making it impossible to stick anything to the tanks. Suction cups probably won't work either.

So to isolate the titanium heater, air stone, and temp sensor, I thought of customizing the following tube (in plexiglass) inspired by commercial heater guards:

Hopefully the numerous slits + open ends allow for sufficient ventilation. Since the tank is only 30cm high, I'd probably only have a water level of max 20cm. I'm aware the octopus can still access the devices via the slits but I feel like this is the best work-around I could think of.? If I add mesh around it, I'm not sure if it will become a hazard? Not sure if I should try to duct tape the air stone too?

Going back to the topic of cleaning the mesh, will detergent actually work? Primarily because it'd be better for the budget :'D As for bead organizers, I got a no-go from my mentor as it'll affect our behavioural study - but I might be modifying the study so this is TBC. Most likely I'll get a few mini PVC couplings to provide shelters for the hatchlings as I read that this can minimize cannibalism. Depending on finalization of the behavioural study, I might need to observe the hatchlings at night for a week or two, so the red light might not be for just a brief period. Yet, IR devices are pretty pricey!

Also, looking around on websites for siphons, there are so many more variations than I expected! Do you reckon this would suffice: Aqua One EasySiphon Aquarium Siphon Hose ? I might just use rubber gloves and pick out discarded shells, but I guess siphons might be required for excrements even for a flow-through system?
The manufacturer got back to me on the slit sizing - they're able to do 0.2mm slits but I reckon this might affect the flow like you mentioned before?
Hi Qiaz!

That's a bummer that you cant affix anything to the inside of the tanks, are you sure suction cups wouldn't work on the inside of the tank? Obviously I don't know the rules of the institution but if they aren't going to allow you then nothing can be done. I think the proposed heater cage design should work well, the only point I would make is to have the temp sensor on the opposite side of the tank than the heater. This will give you a more accurate idea of the actual internal state of the tank. You shouldn't have to worry about the octopus fussing with the temp sensor too much.

I think 0.2mm slits is actually a bit small, and could become dirty more quickly and would be fussy to clean. You are probably okay with 1-3mm slits. The octopus will probably be able to get the tips of their arms into the box (which is almost unavoidable) so just make sure the box is secured in some way so that it cant be dragged around the tank by the animal.

For shell removal, I just use a net but you could pick them out by hand if you'd like. You will probably want a siphon as well just to make sure you can clean the smaller bits out of the tanks. You don't really need a set up as advanced as the one you linked, I just use a tube and my mouth to start the siphon. If you aren't comfortable doing this (I have accidentally gotten tank water in my mouth before) then the siphon you linked should work just fine. If you have a fine enough mesh net you may not even need the tube, but I'm sure it will be helpful in other situations so I would recommend one. The facility may even have some tubes or nets you can use.

I don't think a red light at night should be a problem for the hatchlings. The PVC coupling housings will be better than nothing, but won't guarantee your hatchlings wont get eaten- you'll just have to hope for the best!

Realistically for cleaning the mesh you can probably just use some DI/RO water and scrub the mesh until it looks clean, I wouldn't use detergent on it just in case, but it might be okay to do.
Excellent points, I appreciate it so much thank you!

Yes it's been pretty challenging to adapt to a facility that isn't catered for such work! The tank walls are so heavily crusty with salt remnants I doubt anything can stick to it. I'd try scrubbing them on my next visit but then again with glass tanks I can't use harsh sponges. I might try duct tapes or something, fingers crossed it'd at least stick a bit.

I'd skip the mesh then for the adults, and ask for 2mm slits.
When the eggs are about to hatch, should I add mesh (I bought 200micron mesh) to the heater cage? My main concern is whether it can affect heat dissipation. The hatchlings are about 4mm in length. I reckon I'd change the mesh regularly as you've advised before, for both the cage and the outflow pipe. Will it be an overkill to also add in the commercial heater guards (that the heaters sit in usually) on top of that cage?
The salt creep can probably be taken care of with a wet towel if you use it to soak the salt and then wipe it away. It's frustrating that the facility seems to be under poor care but I suppose you will have to do what you can with the setup you have.

I would do a test run of the heat dissipation with the mesh around the heater cage, with one temperature probe next to the cage, and another on the far side of the tank, near the drain. I don't expect the mesh to give you any issues with heat dissipation but you won't know for sure until you measure the water temp.

Having mesh on the drain screen sounds good to me as well. It will probably have to be cleaned every few days. You can probably just use an old tooth brush to scrub the bits off the mesh without having to remove it from the drain. Depending on how dirty the screen around the heater cage gets, you may have to do a more thorough cleaning but it's hard to say for certain until you have everything set up and see how clean the water is.

I don't understand the part about heater guards. Would you be putting them around the heater? Do you have a photo?
I'll give that a go! Yes completely agree, that's partly why I've been planning this for so long haha. I just hope the octos will be happy with the modifications!🙏

Sounds great, I'll do that in my test runs and scrubbing routine!

What I meant is to use heater guards like these: Aqua One Heater Protector 25 To 300W | Aqua One | Petbarn and then place the protected heater in the slotted cage that I designed earlier for extra protection - or an overkill?

Do I need to adjust the height of the air stone in the tank and transport buckets? I was told that the air bubbles can be detrimental to the octopus as it can enter the mantle and kill them!
Hmm, I think I would be more worried about the heater damaging the housing cage rather than the animals. What material is the slotted cage going to be made of? How warm will you keep the water? What is the temperature of the water that enters the tanks?

If you are making the slotted cage out of PVC plastic you will probably be fine. Its melting point is somewhere between 250-500 F depending on the specific makeup of the material.

There is a chance that bubbles from the airstone could enter the octopuses mantle but it is extremely unlikely. I would be more worried about the bucket airstone than the tank, especially if the airstone is in the slotted cage with the heater. How long are the animals going to be in the transport buckets? Realistically, as long as the airstone is agitating the surface of the water it will be doing its job properly, so it doesn't need to be deeper than an inch or two from the surface to be able to properly off-gas the water.
The slotted cage is purely made of acrylic, I checked that acrylic has a melting point of 320F. The seawater that’s coming in will be during Spring (max 68F) and maybe summer (max 72F). I’ll be setting different tanks at different temps, mainly 66F, 75F and 81F for climate change simulation.

Btw the ‘slotted cage’ I’ve been referring to is the one I designed and attached a picture earlier. The ‘heater guard’ is the one in the PetBarn link. Maybe having an additional heater guard may protect the cage? And the heater guard-in-slotted-cage may help protect the animal?

Would duct-taping the air stone so that it’s just around the water surface be okay for both the buckets and tanks (taped to the slotted cage)? It’s a 20L bucket so I might fill half of it then secure the lid with Velcro. The journey itself is h but I’ll check them every hour or two. So plus rest stops, they will be on the vehicle for about 10-12hours and I’ll be bringing extra tubs of seawater in case of inking.

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