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James' Rearing Chambers

<< Cephalopod Articles | By James and Deborah Wood

Octopus Rearing ChambersThis article will discuss what makes a good octopus rearing chamber, problems I have had with various versions (I still haven't found the perfect rearing chamber) and solutions to some of those problems. At the end of the article, instructions on how to make your own rearing chambers are provided. It is hoped that this article will help aquarists gain an appreciation of one aspect of what it takes to raise marine creatures and I hope it will inspire some to give it a try. While there has been an explosion of interest in marine aquiculture of aquarium fish and invertebrates in the last decade, the number of species that have been raised is a small percentage of those kept and the number of species raised commercially is lower still. There is plenty to be done in this field. Dedicated, advanced hobbyists have a chance to make real headway.

Over the last five or so years, I have put a lot of thought into various ways to mutilate perfectly good PVC pipe, plastic containers that my wife hasn't bolted down, as well as anything else that could potentially be turned into a rearing chamber. While my rearing chambers are specifically designed for the needs of hatchling octopuses, they may be used to raise other mobile benthic marine creatures as well as post settlement larvae. The requirements to rear planktonic marine creatures to settlement are slightly different but many of the main principles still apply.

One of the first decisions one needs to make when rearing marine creatures is whether to batch rear them or rear them in individual containers. Batch rearing is raising several to many animals in the same container. Batch rearing takes less space (i.e. you don't have to explain to your spouse why you have invaded half the house with mutilated plastic containers), is more cost effective (if it works!), and is generally easier than individually rearing young. However, in dense culture, disease and parasites are more likely. Furthermore, with all your eggs in one basket, the risk of epic failure is higher. This could leave you with nothing for your efforts.

Rearing animals in individual rearing chambers takes much more space, time, money, effort and long suffering spouse points (LSSP). However, the risk of disease, parasites, and epic crashes is greatly reduced. Plus the growth and health of individual animals can be tracked and survival rates are usually but not always higher.

The behavior of the animal one is rearing is also an important consideration. For example, adult scarlet lady shrimp (Lysamata spp.) can easily be kept in groups and are found so in nature. On the other hand, banded coral shrimp (Stenopus spp.) that are unpaired will rip each other limb from limb. Obviously, post settlement scarlet lady shrimp are better candidates for batch rearing than post settlement banded coral shrimp. Furthermore, species that school may do better in batch cultures because they may not feel safe if isolated. Animals that are cannibalistic, territorial or aggressive are better off on their own. Hatchling octopuses can be cannibalistic and are prone to disease in dense cultures. Thus there are biological and behavioral reasons to rear them individually.

Another consideration in choosing to batch rear or not is the number of offspring. Obviously it is easier to construct and maintain 25 rearing chambers then 2,500. Another draw back is that these rearing chambers need tank space to sit in. It takes surprisingly few to fill up a standard aquarium so I use 8 foot long by 2 foot wide shallow fiberglass tanks at the University. Finally, one can batch rear part of the brood and rear the other subset in individual rearing chambers.

So what makes a good rearing chamber?We have come up with the following; a good rearing chamber:

1) Physically separates animals
2) Separates the waste water so that it only comes in contact with one animal before returning to the filter
3) Is easy to access
4) Is easy to clean
5) Makes it easy to locate animals
6) Provides the animal with sufficient space
7) Provides the animal with an appropriately enriched environment
8) Is cost effective
9) Is made of non toxic materials
10) Is durable
11) Is escape proof
12) Is able to function in the case of a brief power outage or power surge
13) Has good stable water quality
14) Is easy to check and record water quality parameters

The first and second items on the list reduce disease, many parasites, and cannibalism. They also create some level of independence—i.e. if an animal in container A dies and pollutes the water, the risk of this causing other animals to suffer is greatly reduced as there are no other animals in that chamber and the water will be diluted and filtered before it comes in contact with others.

The chamber should be easy to access and easy to clean. When you have LOTS of chambers to clean and feed you will gain a great appreciation for this point. This is especially true if you are gusty enough to try and maintain some semblance of a normal life while rearing marine creatures.

Being able to find the animals in the rearing chamber is important. Questions such as are the animals feeding, do they have enough food, are they growing, are the chambers clean and are the animals alive are much easier to answer when one can see the little buggers.

The sixth and seventh points are important to the animal's health. Cramped, sterile (i.e. boring) environments can be detrimental to normal development. The animal should have enough space for free range of movement and should be able to hide and explore. This is especially true for 'intelligent' animals such as octopuses. Note that point number seven and item number five often conflict.

The rearing containers should be cost effective. This is particularly important if lots of them are going to be made or you are a poor starving graduate student like me.

It is important that the chambers are made of non toxic materials. If it isn't safe for humans to eat from, don't use it. However, just because it is safe for humans does not mean it is safe for rearing marine creatures. For example, copper that can leach from copper pipes or a copper tea kettle is deadly to most invertebrates. Avoid metals any time you can.

The chambers should be durable. They should be easy to make, able to take some abuse, easy to fix and be constructed of materials that aren't hard to find.

Also, the chambers should be escape proof. This is particularly an issue with octopuses....

While no system is fool proof to a sufficiently talented fool, there are things that can be done to reduce the chance of problems. Try to design your system so that if the power goes off and then comes back on again five minutes later, the flow to your rearing chambers will restart. Be sure to test this by actually turning off and on the power so that you don't get any surprises later. Firmly secure all hoses and siphons; they should be treated as malevolent sentient beings that are just waiting for an opportunity to jump out of your tank and wreak havoc on your floor.

Each chamber should be provided with a reliable supply of good clean water. Ideally this water is straight from the filter (such as a wet dry filter, protein skimmer and/or uv sterilizer) in a closed system or straight from the tap in an open system. There needs to be sufficient flow to change the water in the rearing chamber at least 2 to 3 times in an hour.

Finally, it should be easy to check and record water quality parameters in your rearing chambers. My current rearing chambers are the result of several years trial and error learning and result from both my ideas as well as those of the volunteers that have helped care for my hatchling octopuses over the years. My current rearing chambers are simply the latest version and I'm sure that they will continue to be improved upon. Before I explain how my current brand of rearing chambers are constructed, I'd like to explain some of the things I've tried in the past and what the problems were.

One can make rearing chambers out of a supporting frame and window screening. I view the design of these types of chambers as substandard as they share water and are not independent. However, they do effectively isolate individuals from physical contact. I have never made chambers using this design but have had to temporarily use some already built ones when I ran out of standard chambers.

Various containers such as plastic ice cream containers, plastic butter tubs, and other sacrificial containers can be converted into rearing chambers. However, unless you are only going to make a few rearing chambers you will have to eat a heck of a lot of ice cream and/or set up neighborhood plastic container depots in order to collect enough. Therefore I use 8 inch sections of 4 inch diameter PVC pipe.

I spent a lot of time, way too much time actually, trying to find the perfect glue to attach the screening to the bottom of the PVC pipe sections. I didn't want to use silicon at first because it doesn't make a strong chemical bond so I tried epoxy. The problem with epoxy is that while it is strong, it is hard to get every little bit glued down. Furthermore, the little 1/8 inch bits that aren't glued down are hard to find, at least for humans. Octopuses seem to have no trouble at all finding them....

So, in a bit of a panic as I had 200 plus deep-sea octopus eggs hatching at the moment, the next thing I did was go to a hardware store and ask for something that would glue my screening to PVC pipe so that it stayed glued. They gave me a calking tube of... I'm not sure what it was but the stuff was baby puke yellow and boy did it stick well. It didn't come off one's hands and it smelled 'chemical'. This stuff definitely held on to anything but I was a bit worried that it might be toxic so I put a few of my new rearing chambers in a bucket with sea water and a few amphipods. The amphipods died. I tried to scrape all the hardened glue off of one of the rearing chambers but the stuff was everywhere so I chucked them all and started again. This time I used plain aquarium safe silicon sealant. While not as strong as the former two, it was safe and it was easy to see when its hold onto the cloth was breached. One would think that I'd been doing this sort of thing long enough by now not to try and use questionable materials to build rearing chambers—I guess some lessons one has to learn more than once.

For a lid, I initially used window screen fastened with a rubber band. This allowed easy viewing of the octopus without removing the lid. However, while the octopuses didn't escape out of the top, they did occasionally crawl up the side and lodge themselves on the outside of the chamber where the screen was held with the rubber band. There they would desiccate and die. A partial solution was to use PVC pipe connectors to hold the screening on. This eliminated the gap in which the octopuses would desiccate.

Still, some octopuses (particularly the Florida pygmy octopus, Octopus joubini) would occasionally crawl up the container and dry out on the side—often a mere inch or two from the water below! This sort of suicidal behavior is very frustrating!At first I though that I must have some sort of water quality problem. Eventually I added some floating corks and crumpled bits of plastic 2 liter pop bottles and this suicidal behavior stopped. What I now know but didn't know then is that O. joubini likes to hide a lot; apparently they did not feel secure in the sterile environment that I had previously provided. Although the cut soda bottles did make the animals feel more secure, they also made it harder to see and catch them as well as harder to clean the chambers. However, I used the green opaque plastic which was a good compromise between the total darkness that the octopuses would have preferred and my need to check up on them.

Originally the ends of the 1/8 siphons that bring water from the filter to the rearing chambers were placed below the water level in the rearing chambers. This was done so that the siphons would not break during a power outage. Almost immediately some of the live food (amphipods) started going up the siphons. As the amphipods were small (and didn't seem to restrict water flow) and easy to collect I didn't think much of it. About a week later several of the octopuses all at once (are they unionized???) decided to crawl up into the 1/8 siphons. Needless to say, getting a hatchling octopus out of a 1/8 inch tube without damaging it is a challenge.

We raised the end of the siphon an inch higher than the water level in the rearing chamber. The narrowness of 1/8 inch tubing often prevents air from getting into the siphon, especially if the end of the siphon is near the water level. This is important so the siphons will restart after a power outage. As mentioned above, designing a system that will self start in case of a power outage is an important consideration.

And now what you have been waiting for, detailed instructions on how to make your very own rearing chambers. An exploded diagram of this contraption is shown in figure one. Start with a perfectly good section of 4 inch diameter PVC pipe. Don't be tempted to save money by using anything narrower than four inches as it will be hard to see into, hard to clean, and hard to catch the little buggers if you need to. Wider pipe can be used but it will cost more. Now cut your pipe into 8 inch sections and sand the ends to make them smooth. Be sure to wear safety glasses and to retain your fingers while cutting and sanding your pipe sections.

Next, get some screening cloth fine enough that it will retain your animals and their food but still allow good water flow. Window sheers seem to be working the best. The cloth you use shouldn't be cotton or anything that will rot and it should be fairly strong so that it doesn't easily rip like nylon stockings. You should be able to pick this stuff up at a cloth store; if not you can always cannibalize your wife's wedding dress (just kidding, sheesh!). Cut the cloth into 5 by 5 inch pieces and glue it onto the bottom of the PVC pipe with aquarium safe sealant. Another option is to secure the cloth onto the bottom of the pipe with a PVC pipe connector.

So, now you have an 8 inch section of PVC pipe with screening attached to the bottom. Now add a 1/8 inch siphon bringing clean water to each of your rearing chambers. At this point you might be done. However, if whatever it is you are rearing is likely to escape out the top of the rearing chamber or if it or whatever you are feeding it is likely to go up into the siphon you will need to continue. Figure one demonstrates 1) what your contraption should look like at this point and 2) that creatures such as octopuses, even stuffed ones, are not likely to stay inside your containers with out a lid.

A lid will solve these problems although it may make it harder to see the animals. My lids are constructed of four parts, a 5 by 5 inch section of screening cloth, an old flat cork (a bunch of these were being thrown away by the department, other things can be used as substitutes), a four inch section of ridged 1/8 inch tubing, and a 4in PVC pipe connecter. As the pipe connectors are expensive (well, when you need 100 of them they are) I cut them in half (then you only need 50 for 100 chambers). Next, glue the cork to the middle of the screening. Then drill a hole through the middle of the cork and screening and insert the 1/8 inch ridged tubing leaving about an inch above the cork so that you can connect your siphon. Place the screening on top of a rearing chamber, slide on the pipe connecter to hold it in place and presto, you have a lid that both seals well and is easy to remove.

The final step is to add all your new rearing chambers to your system (remember I did mention that using individual rearing chambers takes a lot of space) and populate them with beasties. Well, there you have it, an in depth behind the scenes look at what some of us do to otherwise innocent and whole pieces of perfectly good PVC pipe. Happy rearing.

Articles Reference

Wood, J. B. and Wood, D. A. 1998 James's Rearing Chambers. Freshwater and Marine Aquarium Magazine. vol 21, no 12. Reprinted in: The Cephalopod Page (http://www.thecephalopodpage.org/index.html). Wood, J. B. Ed.

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The Cephalopod Page (TCP), © Copyright 1995-2014, was created and is maintained by Dr. James B. Wood, Associate Director of the Waikiki Aquarium which is part of the University of Hawaii. Please see the FAQs page for cephalopod questions, Marine Invertebrates of Bermuda for information on other invertebrates, and MarineBio.org and the Census of Marine Life for general information on marine biology.