HCA: Hermit Crab Association

Hello people

I'm not even a crab owner, although I might become one. Somehow I've gotten into my head that trying to build the ultimate terrarium would be a cool thing to do, and since I never even had one (only had a huge aquarium when I was a kid) I did not even knew what kind of habitats that folks usually build, how they worked or even for what kind of animals. I sort of needed a animal to aim for, to spec this ultimate DIY-contraption of mine for…

Then I came across Coenobita and it's crazy keepers

What a cool little creature! And hermits seemed to actually require quite a lot from its surroundings, much harder to "do right" than most other things you keep in a terrarium. That's pretty ironic considering hermits, if I have understood it correctly, often are mistook for an easy-to-handle-children's pet, almost a toy.

Still it suited me, it was small and made for some interesting challenges when it came to temperature, humidity, physical enclosure and water-requirements. My first goal is to build a small (very small!) prototype of a working system. No regards for how things look, or how practical they are to handle, just a platform that I can learn from. Learning how to do things is where the fun is. The road is the goal for me.

A crabitat built from scratch thats supposed to be "ultimate" in any way is a very multifaceted thing. I need to learn a lot, and I need to get good at a lot of practical things along the way. The requirements of the crabs is of course on the top of the list, but they are still only one facet. Even for a guy that hardly know what relative humidity is or know the first thing about how to heat a tank it's possible to learn and build something thats better than any off-the-shelf solution. What I can't learn is experience in keeping hermits.

Thats why I'm here! I'm basically just going pick your brains on all things practical when it comes to hermits, their handling and behavior. Hopefully some of my ideas could be interesting for you experienced folks too. I'm a systems developer by trade, so this is just a excuse to learn new tech and to make something that could be simple into an extremely complex monster. Kidding about the last part, we don't do that... So much.

I don't have any pictures to post yet, but to give you a idea here's the spec for that first prototype that I have in my head:

• Conform to the normal requirements for hermits (fresh & ocean water, deep substrate, shelter, temp/humidity etc, etc…)
• Small size, I need to be able to move it around.
• Working, ie. when finished, I could put in some very small crabs there and they would do great
• Automatic controlled temperature and humidity
• Automatic top-up of water (at least fresh)
• Day/night temp and light cycle.
• Easy way to change water and clean
• Groovy design (if you build it from scratch, no need for it to look normal ) but still functional
• Efficient, that is, as low power- and water-consumption as possible.
• Multi-level but easy to access
• Wide range of temp and humidity (not needed for crabs, but I want the possibility and performance)

A lot of things gets much more complicated when they need to be small, so many of the things I want to implement will get interesting just due to the form-factor. But if/when I have the prototype ready I can choose to scale it up for a "real" sized enclosure if I want.

Lastly a few things about the intended design and features, as far as I have come.

• It's going to be a corner-tank with rounded glass on the front, think a 90deg pizza slice.
• Built in plywood and acrylic (want to be able to form bend the glass at home)
• In-tank heater. Probably a DIY integrated in the enclosure
• Vertical, ie. a very small footprint to height/volume ratio.
• Pools in several levels.
• Some kind of circulation of the water - either a drop-system or a full waterfall
• Maybe some miniature filtration of the water to make it last longer (not sure its worth it tho)

I'll get back with some pictures of my experiments when I have them.

You sound more like an engineer than a systems developer ( from the "to make something that could be simple into an extremely complex monster.") ! This sounds VERY interesting and I can't wait to see what you come up with!

I haven't been at it long, but I wonder if the in-tank heater might be a problem. We all use side-mounted under tank heaters (people who have reptiles use them under the tank...hermits, needing at least 6" of sand/substrate, can't have all that heat under them or they will cook and the sand will dry out, so we put them on the sides of the tank.

I would like to see what you come up wioth for the humidity factor. They need humidity of around 80%, and to get that, most of us use little tubs of damp moss, plus either mist the tank a couple of times a time, have bubblers in our pools, etc. Some use humidifiers piped into the tank (expensive). I always thought there might be a better way!

I look forward to your "crazy man's tank", and when your design is complete, well, then you HAVE to get some crabs, because they will be your ultimate deciding factor!

You definitely came to the right place to learn all about hermit crabs.

However, I do want to throw back a few things for you to consider. What you're describing sounds like a tall, narrow, and relatively small enclosure. While these are beautiful tanks to look at, they aren't exactly ideal for hermit crabs. With crabs, the number one most important thing to provide them is with space to molt safely. That requires a rather substantial footprint per crab, and a lot of heavy moist substrate. What dimensions are you thinking of making this? If it's not large enough to fit several crabs, then there will be little daily activity going on to watch.

hermieluv1 wrote:I haven't been at it long, but I wonder if the in-tank heater might be a problem. We all use side-mounted under tank heaters (people who have reptiles use them under the tank...hermits, needing at least 6" of sand/substrate, can't have all that heat under them or they will cook and the sand will dry out, so we put them on the sides of the tank.

This is exactly the kind of feedback I'm after. Yes, there's probably a reason why a side-mounted UTH is the normal way to do it for hermits. What the thick substrate really becomes is insulation, so if you place it under that tank you have to "heat through" it to get the temperature up in the tank. No good. And with a clean tank (no insulating backgrounds) the bottom is really the only side that have any insulation at all, which makes it especially inefficient.

"Don't heat the substrate" is what you are saying I guess. Got ya! I will investigate how I can incorporate a heater into the design, since I will have insulating walls i can't put it outside.

hermieluv1 wrote:I would like to see what you come up wioth for the humidity factor. They need humidity of around 80%, and to get that, most of us use little tubs of damp moss, plus either mist the tank a couple of times a time, have bubblers in our pools, etc. Some use humidifiers piped into the tank (expensive). I always thought there might be a better way!

Humidity is an interesting thing. You can get the humidity up by just adding water to naturally evaporate (moss, misting, water-buckets, etc..) but only so much. And the tiniest of ventilation quickly kills it. One of my first findings was just how big difference even small air-leaks makes for what kind of levels you can get. I *think* creating a more air-tight enclosure is the first thing to consider. I have not decided on exactly how to do this myself, but I think you are right, theres have to be something thats between just a bubbler and a full blown cold mist system.

hermieluv1 wrote:I look forward to your "crazy man's tank", and when your design is complete, well, then you HAVE to get some crabs, because they will be your ultimate deciding factor!

For sure. Even tho in my case, I suspect the poor things will be more of test pilots than pets

wodesorel wrote:You definitely came to the right place to learn all about hermit crabs.

Yea, I've already learned tons just by reading here. Thanx for all that info btw.

wodesorel wrote:However, I do want to throw back a few things for you to consider. What you're describing sounds like a tall, narrow, and relatively small enclosure. While these are beautiful tanks to look at, they aren't exactly ideal for hermit crabs. With crabs, the number one most important thing to provide them is with space to molt safely. That requires a rather substantial footprint per crab, and a lot of heavy moist substrate. What dimensions are you thinking of making this? If it's not large enough to fit several crabs, then there will be little daily activity going on to watch.

I'm know about the molting, but I hadn't connected the dots that that's part of the reason why people keep so many crabs.

But yes, you are correct, the tall, narrow format doesn't make for much area for molting. My prototype enclosure I have now just to test stuff out in is 8x8 and 24 inch high. It would probably be just big enough for only three tiny crabs if I was to build it proper. I most likely need to either scale up, or live with a very limited number of crabs. Maybe both if I want to stick to the "tower" design.

Good input, thank you.

hermieluv1 wrote:I haven't been at it long, but I wonder if the in-tank heater might be a problem. We all use side-mounted under tank heaters (people who have reptiles use them under the tank...hermits, needing at least 6" of sand/substrate, can't have all that heat under them or they will cook and the sand will dry out, so we put them on the sides of the tank.

I don't see why an in-tank heater would be a problem. I plan on putting a radiant heat panel on the inside of my new 90 gallon tank. It costs a little more in the end, but it will last longer, are more adjustable, keep its value if I ever need to sell it, and wouldn't dry out the substrate like a heat lamp does in my experience. Plus, if I upgrade again, I can reuse it, while UTHs are always adaptable to the new tank and/or cannot be removed easily without the risk of damaging it.

http://www.reptilebasics.com/80-watt-radiant-heat-panel

For my tank in specific, this one would heat it more than sufficiently. It is just important you use a thermostat, so you can control the temperatures. You can use them without, but obviously if it was too hot, you couldn't turn it down. It is going to cost just as much, if not more for me to use UTHs, that still might not provide enough heat, even after insulation due to the weather fluctuations where I live and the size of the tank in general.

72mm wrote: But yes, you are correct, the tall, narrow format doesn't make for much area for molting. My prototype enclosure I have now just to test stuff out in is 8x8 and 24 inch high. It would probably be just big enough for only three tiny crabs if I was to build it proper. I most likely need to either scale up, or live with a very limited number of crabs. Maybe both if I want to stick to the "tower" design.

And 8x8 space is smaller than the footprint of a 2.5 gallon. It's about the size of a kritter keeper, so that would be too small to house hermit crabs, if you wanted to start them off in your prototype. The height is nice and very generous, but small crabs aren't going to be able to utilize it the same was as larger crabs as while they do climb, they spend most of their lives under cover for safety until they can grow larger.

There's not many living things that would be content in that narrow of a home.... Maybe look into mantids? There are some awesome exotics out there and I believe they need vertical space. The only downside is that they have short lifespans.

IMO the way you're talking about building and testing everything out just really doesn't sound like it's in the best interests of the crabs. I don't mean to sound harsh but if you "suspect the poor things will be more of test pilots than pets" maybe you should try something other than hermit crabs. As wodesorel said, there are mantids or other insects that are interesting and exotic and would be more suited to a smaller vertical space.

Breeezy wrote: I don't see why an in-tank heater would be a problem. I plan on putting a radiant heat panel on the inside of my new 90 gallon tank. It costs a little more in the end, but it will last longer, are more adjustable, keep its value if I ever need to sell it, and wouldn't dry out the substrate like a heat lamp does in my experience. Plus, if I upgrade again, I can reuse it, while UTHs are always adaptable to the new tank and/or cannot be removed easily without the risk of damaging it.

Radiant heat panels sounds interesting, I'll have to read up on how they work. Haven't given much thought at how to heat things tbh. I figured with good enough spread of heat from the source and good isolation I could get away with quote few watts.

wodesorel wrote:And 8x8 space is smaller than the footprint of a 2.5 gallon. It's about the size of a kritter keeper, so that would be too small to house hermit crabs, if you wanted to start them off in your prototype.

Well, that was the idea. Not needed tho, I'll just scale it up to whatever size is needed before I put any crabs in there. It's a prototype to play with the technical stuff after all.

wodesorel wrote:The height is nice and very generous, but small crabs aren't going to be able to utilize it the same was as larger crabs as while they do climb, they spend most of their lives under cover for safety until they can grow larger.

With "small crabs" you mean young crabs? It's often the same I guess. Do young/small crabs climb less as a rule?

soilentgringa wrote:IMO the way you're talking about building and testing everything out just really doesn't sound like it's in the best interests of the crabs. I don't mean to sound harsh but if you "suspect the poor things will be more of test pilots than pets" maybe you should try something other than hermit crabs.

Well, to be brutally honest the best thing for the crabs would be if we left them alone in their natural habitat and did not create a market on the other side of the world by putting them in tanks in the first place. They are all just collected from the wild and shipped to where people want them. I don't think we really want to know how many crabs have died in that process for each one that make it alive to one of our tanks. Sorry if I sound harsh, but I think thats the truth of it.

soilentgringa wrote:As wodesorel said, there are mantids or other insects that are interesting and exotic and would be more suited to a smaller vertical space.

Well, as long as the bottom-area is large enough, I don't see why a crab-tank could not be vertical. They dig, thats vertical. They climb, thats vertical. And as I've heard from stories here, they seem to explore vertically just as much as horizontally. Besides, insects don't interest me enough to make me want to build something for them...

72mm wrote: Well, to be brutally honest the best thing for the crabs would be if we left them alone in their natural habitat and did not create a market on the other side of the world by putting them in tanks in the first place. They are all just collected from the wild and shipped to where people want them. I don't think we really want to know how many crabs have died in that process for each one that make it alive to one of our tanks. Sorry if I sound harsh, but I think thats the truth of it.

Keep watch in our adoption section or Facebook page for hermit crabs that need a new home in your area. That way you're not supporting the collection of more hermit crabs from the wild. When you're all set up and ready for crabs, you can also make a post in the thread for your location stating you're looking to adopt with info on your crabitat.

Because of their molting needs, the total number of crabs has to be based on the footprint of the tank and not how tall it is, since they spread out horizontally to stay away from each other. This is especially true since most will dig to the very bottom and will all be on the same plain, instead of being interspersed throughout the substrate randomly. We have a guide that covers how many crabs per gallon is comfortable, based on their size. It also gives the minimum tank size for the size of the crab - and that's based off the length and depth of a standard aquarium. Use those standard aquarium dimensions when figuring how big to make your finished enclosure and how many crabs of a certain size would be happy in there. Our minimum tank sizes start at a dimension of about 16x10, which is a 5 gallon. Keep in mind that crabs grow extremely quickly, and a micro crab will outgrow a 5 gallon tank in one to two years, and a small crab will outgrow a 10 gallon tank in around two years. This is the link to the crab per gallon guide, and it has links to standard aquarium dimensions: http://hermitcrabassociation.com/phpBB/ ... 26&t=92541

And yes, smaller crabs are younger and they do tend to climb a lot less. They also molt once a month, and tend to hide a lot for protection. Where they come from, everything is trying to eat them. They spend all their time and energy trying to get as big as possible as fast as possible.

CallaLily wrote:Keep watch in our adoption section or Facebook page for hermit crabs that need a new home in your area. That way you're not supporting the collection of more hermit crabs from the wild. When you're all set up and ready for crabs, you can also make a post in the thread for your location stating you're looking to adopt with info on your crabitat.

A very good idea. Thank you.