Crazy mans crabitat?

[72mm]

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.

Yes, which means that a vertical design must be bigger per design than the comparable "normal" tank to be good for hermits. That's the opposite of what I wanted, which is "good, but small so I can move it". Important realization to have early in a project.

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.

Their molting behavior is especially interesting. Would the fact that they often dig as far as they can indicate that they really want (I won't say "need" because the dangers in captivity is totally different than in the wild) even deeper substrate? They obviously dig for protection during the molt, but could it be that they also want the added humidity? One would think that to have a as stable climate as possible would be really important during molting.

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

I've read it, thanx.

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.

Makes sense.

[wodesorel]

No one has really studied molting crabs in the wild since it's impossible to track individuals and it's hard to locate where they dig to molt. We have no idea how far down they can get when there is no bottom to stop them, but you're right in that it's likely to be deep both for protection from other crabs and predators and because of the stability it offers. They are stuck wherever they choose to molt for weeks and sometimes months, so it has to be a safe location. I've always figured that's the reason why some crabs will spend weeks before the actual act of molting just sitting underground, or moving around from place to place - they're making sure the spot they've chosen isn't going to flood or dry out too much or be discovered while they're vulnerable.

[72mm]

No one has really studied molting crabs in the wild since it's impossible to track individuals and it's hard to locate where they dig to molt. We have no idea how far down they can get when there is no bottom to stop them, but you're right in that it's likely to be deep both for protection from other crabs and predators and because of the stability it offers. They are stuck wherever they choose to molt for weeks and sometimes months, so it has to be a safe location. I've always figured that's the reason why some crabs will spend weeks before the actual act of molting just sitting underground, or moving around from place to place - they're making sure the spot they've chosen isn't going to flood or dry out too much or be discovered while they're vulnerable.

Yep, I'm sure they explore below ground almost as much as they seem to do above. I guess they tend to stay away from the glass so you can't really watch them when they are down in a tat?

[72mm]

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 have not put much thinking into the heating part yet. Basic idea is that as long as tyne tank is isolated and I have control over ventilation basically any type of heat-source would do as long as it doesn't have to transfer heat through the substrate (thats whats drying it out). I figured i just get a heat mat or heat tape and build that into the sides of the thing. For my prototype i have a old style lightbulb encapsulated in a small housing which transfers heat out into two copper-plates (nothing living in there, so I can use as toxic materials I want for experimentation). This to sort of simulate the kind of heat source a heat mat or tape is. With holes in the housing for the lamp I also created a natural airflow heating the air as it passed through. I even had plans on warming water in there because its so much more efficient than warming air. I wanted to be able to experiment with this kind of things to get a handle on how to best do it.

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 started experimenting with this. Goal was to come up with some sort of contraption that was not too complicated that could be used to control humidity in my prototype box. Even if I got to a point where I could control temperature and set humidity to anywhere between 40 and 80 and it would keep it there, this is not relevant for a real enclosure where you have all this water and moist substrate that adds to the humidity. Just limiting the ventilation should be enough for keeping humidity I think, no real need to actually humidify the air further.

Since I plan on having flowing water (waterfall, stream) I should not really have any problem with humidity, starting to design a humidifier was probably wasted time for my particular build, but I learned a lot about how it works. Bottom line for humidifying air by forced evaporation is simply wet surface-area and air-flow. My last design for a DIY humidifier was half of a 2L Coke PET-bottle full of wet pebbles of the the light, ceramic brown type you use for plants + a fan (computer chassi-type) blowing air through the whole thing. If you can keep the pebbles wet and got room for it inside the enclosure, thats pretty effective. My guess is that any added airflow over any wet or moist surfaces will be highly effective in driving humidity up in a tank. This will off course dry that surface, which might be a problem. You still would need to get water into the tank, but you would get a much more effective evaporation.

When I took a step back, I realized that I should have started with the water-system instead. IF you going to have flowing water, I suspect both the heating and the humidification can be based around that fact. The thing is, if you showed my PET-bottle to a aquarist chances are he would say it was a strange attempt at building a trickle filter. A trickle filter is a type of biological filtration for aquariums. One of the listed downsides of these filters are water-evaporation, that is, they tend to put a lot of water into the air... If you showed the same thing to a engineer working at a nuclear power-plant he would identify it as a model of a cooling-tower

Funny how the same thing can be different things depending on your POV.