Kreiselponics? Blending Hermit Crabs with Aquaponics and Retail.

[Daniel of Windsor]

Hello HCA,

A little bit about myself:

My name is Daniel, I'm from Windsor Ontario, and I'm looking to dip my toe into owning a small herd of hermit crabs for my living room at some point in 2023 or 2024, pending financial circumstances. I have previous life experience as a small cage bird owner and breeder (finches mostly...), and since bird flu is all the global rage at the moment, I don't see how I can safely continue my backyard hummingbird & oriole project this year. As a person of allergies, cats and dogs and rodents aren't going to happen, and Canada has a hard bias against reptiles and insects because of a lot of very old and outdated venom and bacteria misconceptions. This means that if it's not in the local PetSmart, I can't have it. As a person of visual disability, small fish are, well, too small. This means hermit crabs or unicorns, I guess? I enjoy the activity of habitat building, I like watching animals use what I build for them, so I fully intend to exploit hermit crabs as though they were a troop of my very own personal show monkeys, as slow as they may be about it. Plus it gives me the excuse to build an indoor garden, where disease carrying wild rats with wings won't come anywhere near me, even one that's confined to a humidity-sealed tank I would be ok with that.

Upon starting my research, some light reading and video watching at the moment, I came across the exciting new venture that seems to be hermit crab breeding. So far, everything seems to indicate that it's a lovingly royal pain in the dedicated butt to do, as it requires extensive water changes and re-inventing the kreisel. From where I'm sitting, that just seems like too much work for too little babies. So I got to thinking, how could I re-invent the system? I came up with an imaginary theory, and I want to pass it through you guys for your thoughts.

Kreiselponics?

Floorspace wise, let's imagine you have either a two-car garage or an empty basement. Imagine an upside-down horseshoe, the bottom left has a giant saltwater kreisel tank, and at the bottom right has a freshwater pool. From the kreisel tank going upwards on the left side is a saltwater aquaponics system. As for the plants, I'm looking at Batis https://en.wikipedia.org/wiki/Batis_(plant) and Sea Purslane https://en.wikipedia.org/wiki/Sea_purslane as a group of potential candidates, given that they're low growing, perennial or evergreen, and edible, the idea being that hermit crabs can safely eat them, I hope. What I can't decide on is the correct substrate, something perhaps to the effect of 70% glass stones (bottom layer) to 30% detritus (top layer) because saltwater will inherently want to lose its salt by percolation, hence the non-sticking glass stones for easy replacement-cleaning and only sufficient detritus for the plants whereas their roots will reach the glass stones to do their filtration work, which will certainly need replacement once a year as marine salt should cake the detritus layer, hence a hardy perennial or evergreen is essential for transplanting. This is important to note as at the beginning of any water change, you'll lose salt at first gradually as it gets filtered-out until saturation begets balance, and then on any random day a bunch of salt might suddenly re-enter the water flow if the substrate gets disturbed, so rapid salt-mass imbalance is a possibility to watch out for. Assuming it wants to stabilize by virtue of its size however, on its own, this could constitute a "starter package" for doing only hermit crab breeding and baby selling, just add all the other creature comforts required, and a climb-out mesh connecting the kreisel and a kitty-litter bin sized sandbox etc..

Now let's make some more money, by adding a connecting table from the left top of the saltwater aquaponics system going to the right top of the freshwater aquaponics system, this middle table will constitute our "bird and bug" (or "chameleon/gecko and bug") area. An idea hit me, what other species might be compatible with hermit crabs, and can we breed those in the same enclosure ecosystem? Much like how the saltwater aquaponics system will basically be poop-duty free save for some spot cleaning on the leaves and a periodical over-salted detritus change, why can't hermit crabs also be put on poop-duty too? If we consider the table as "ground level", I can easily see somebody who is raising rubber ducky isopods and other bioactive insects to use this space for additional pet store retail fodder, and these insects love eating poop of all kinds. So, let's source it from the "airspace level" with some cage-bar bottomed canary breeder cages that are seated above the table, spilling poop and feathers and seeds down onto the table. Now, you might think yuck, but bird poop has some serious amino acids and other vitamins and nutrients, as does spilled bird seed and feathers which adds carbohydrates, keratin and calcium. As odd as it may seem, I can image a hermit crab may be tempted to nibble on the odd molted feather or crop grain it can get its claws onto, as it may in the wild? At the very least, meanwhile between hermit crab breeding seasons, hermit crabs can still eat the isopods and other insects that just became gut loaded on bird goodies, you can sell those same rare bugs and the various canaries to keep the set-up slightly profitable at the very least, and this area will be easy to clean at any time for any reason, but you likely may not if it can be used as a bioactive preservation zone. Having a dry land area for springtails to then traverse into the vegetation of the saltwater and freshwater aquaponics zones, will help to keep mold down considerably.

Which brings us to the right side of the upside-down horseshoe, going downwards along our freshwater aquaponics system, is basically anything you want that's safe for hermit crabs to eat, and some goodies for the other humans in your family as well, let's not forget to feed those too! Keeping in mind that hermit crabs like to climb, I think some dwarf thornless berry bushes are in order? If you're a nutritionist, food for hermit crabs, birds, insects, and you'd never need to buy pet store food ever again! Or, so long as the plant is safe, some plants are good to harvest essential oils from, so the ability to make your own massage oils, skin creams, incense, body soaps, scented candles, doing this can help pay to keep the breeding project further going still, while adding more crawling room for your hermit crabs to get exercise in. A free-roaming crab is a healthier crab after all, and it's in this area that an empty pit in the substrate allows for freshwater access, such as in a submerged pasta strainer for example. This just leaves to question what you'll do for the fish pool? Do you want tilapia for yourself, some goldfish for a meditation space, or will you connect it to a wall of aquariums for even more pet store fish that you can breed and sell? The options are endless, the scale-up choice is yours.

Questions.

As for all the plumbing and electrical to make this work, I'm not there yet. I'm just sharing the imaginary idea so you can understand the questions I want to ask:

1: How large can a kreisel reliably get, and in a free-range setting where the hermit crab female can crawl themselves into a kriesel for laying, does the kriesel size limit the amount of females one should have in any enclosure; what's a good ratio?
2: Being that, do all the females come into laying at the same time, or is it staggered over a period of months, and can multiple generations of babies at different growth rates safely occupy the same kreisel? Even if not, as being at risk of cannibalism, maybe they should, if the idea is to not be overburdened with the success of too many babies in one go, why shouldn't the bigger ones get some nutrients from eating the smaller ones, if this improves the survival rate of the larger ones?
3: Assuming it works, that the saltwater/"beach water" plants filter the toxins out of the water as an aquaponics system inherently wants to do, this just leaves the scum of the tank because of all the detritus, so are snails and cleaner shrimps safe for a kriesel tank as "the nursery crew", selecting the smallest snails possible so as to harvest their shells for the hermit crab babies?
4: By keeping hermit crabs in a saltwater aquaponics environment, considering that a plastic mesh cup stuffed into the substrate could allow a saltwater pool to be made for terrestrial submersion in lieu for the conventional saltwater dish, would this help to protect the hermit crabs from parasites, even if should they venture into the bioactive bird and bug table as well as the freshwater aquaponics environment, as such nasties inherently don't like saltwater anyways?
5: Has anybody formulated a "perfect diet" of insects for protein and plants for everything else, and has anybody tested hermit crabs for compatibility with insect species, bird droppings, bird seed, bird feathers?
6: Has anybody done testing for Batis and Sea Purslane as compatible plants, and has anybody ever done any aquaponics of any kind on hermit crabs before, seeing as that they have the potential to be one heck of a clean-up crew for spilled food waste and plant pests, such as land snails and slugs and bugs on crops?

7: Give me your top 10 books I should read, top 10 videos I should watch, and top 10 things I ought to know. Give me homework and other ideas I've yet to consider. I won't be acquiring hermit crabs for a few more months at the very least, so I'm studying and planning it out until then.

Thank you for hosting what is surely a bunch of really odd questions and ideas, please forgive my noobness.

[IamSam]

I don't think you can reliably predict or coax hermit crabs into breeding like you can with other animals. You can give them ideal conditions and a second salt water pool and hope for the best. There are those who have ventured into baby hermit crab raising who have had both successes and misses. But in any case first your hermit crabs will need to feel comfortable in their enclosure and anyone with crabs can tell you that just getting your crabs through their first moult can be more stressful then you would expect.

I'm excited that your looking into 'building a better mousetrap' as they say. Since captive breeding hermit crabs is so difficult any creative people dedicated to improve sounds awesome. Getting your hermit crabs comfortable and through pps is the obvious first step.
For the rest we have a care sheet for breeding,
https://www.hermitcrabassociation.com/p ... hp?t=92518
Crabcentralstation has a lot of videos about their crabs breeding on youtube,
https://m.youtube.com/@CrabCentraYouTube,
And you could explore the breeding section of out topic categories,
https://www.hermitcrabassociation.com/p ... .php?f=123

I've read some people's experiences online and your idea of a mainly(correct me if I'm wrong) self sustainable hermit crab baby farm is cool.
I worry that with your setup that water changes may be difficult.
And I read on one person's (I forget who) one thing they were having trouble with was getting the baby crabs to go onto dry land. This is obviously much later in the baby raising process. But it did make me think that they might be coaxed onto land more effectively if their were some artificial waves happening to coax them ashore? Just a thought.
And please don't forget hermit crabs are prey animals and many things will want to eat them and depending on the species they spend more or less time in the pools. For example, Purple pinchers are more of a sit on the edge and stick a toe in type whilst others enjoy a swim. land hermit crabs do breath through modified gills and can stay under water for a good amount of time but they can still drown so make sure they have a way to get out of the pools.
It seems you are looking at this potential setup as a combination passion project/investment, which is totally cool. And I hope it works out for you.