Not sure how to use space

[EliSH]

Hello, my name is Eli

So I've had hermit crabs for about a year. Before now I had two purple pinchers in a 20 gal tank. It was all I could manage at the time. When I moved, I took with me and old tank I used to keep mice in (I made sure to clean and air out very well before setting up for hermit crabs). Unfortunately, I got it off of Facebook marketplace, so it was used when I got it and I'm not sure if the size in terms of gallons. It's 36 inches long, 18 inches wide, and a foot tall. I've got it set up on an old desk at my new place but I've run into a problem, with all the substrate, it leaves only six inches of height for everything else, which is very small. I figured I'd do a gradient, I have three crabs now after rescuing one from an owner who had no clue what she was doing, so I figured if I give them a large area (about half the length) of 6 inch substrate, they'd be able to find a place to molt. Then I'd do a gradual slope down to about 2 inches of substrate so I can put pools, their cork log, abd all of their other important stuff. But looking around I've never seen anyone do this, it's always the same amount of substrate throughout, so Im worried there is like a reason no one does it. Can I do this without hurting my Crab's ability to molt/tunnel? If not how can I use this space in a smart way so they get all of their needs met?

[DragonsFly]

You can do this; just don't put any more crabs in. Sounds like you have a 30 gallon breeder there; the breeders (as you can see) are not the greatest arrangement of volume for crabs because height is key for crabs to allow for depth of substrate and some climbing options. However, you could consider adding a "topper" or even two, to add some height.

I have a gradient in my 120g high, but not as steep as that. My "jungle end" (EE and playsand, where the fresh water source is) is about a foot or a little more deep, sloping down to the "beach end" (play sand only, where the MSW source is) which is about 9 or 10 inches deep. It has settled since I put it in at about 15 inches sloping down to 12 or so; I'll add some more as soon as Major Tom comes back up (taking his LOOOOONG time). The thing is that your crabs will likely dig and "earthmove," so if your gradient is really steep, you probably won't be able to maintain it very well; the substrate will tend to make its way down the slope, and if you have both pools down there, it might eventually drive you nuts that the pools are always full of substrate. . . . But if you only have 3 crabs and they are not too "diggy" all the time, it might be fine. Some are more climbers than diggers, especially if you give them lots of places to hide in the climbing structures; some dig down every day and come back up and out at night, keeping the substrate disturbed all the time. My two have not done much to disturb my slope, but again, my slope is not as steep as what you are considering. Also, Billie Jean (the only one up now, for going on two years now) is the "climber" type, so she basically only digs when she is thinking about molting. When (if?) Major Tom ever comes back up, he tends to be more the "digger" sort, so we'll see if he proceeds to excavate all over the place and ruin my nice "jungle" and "beach" theme.

Bear in mind, too, that no matter how much substrate you have, there is always a sad possibility that one will encounter another in a vulnerable stage of molting. The idea is to minimize that chance, though, by maximizing substrate volume (both "footprint" and depth), and minimizing the number of crabs you confine together.

[EliSH]

I've seen people who have toppers, have no idea how to go about putting on up tho, I will definitely look into that, expecially since one of my crabs is a digger, the 20 gal was always a mess because he would just dig pits

[DragonsFly]

I looked at standard tank measurements and don't see one that would be smaller than your tank but 18 inch wide, unfortunately. Sometimes, you can find a smaller size tank that is the same width as your bigger tank, and just turn it upside down on top of part of your bigger tank; voila, a topper! But it apparently won't be that easy to top this breeder. Maybe somebody who knows more about different types of tanks can suggest one that would make a ready-made topper. Otherwise, you can make one from sheets of acrylic if you are the handy type.

[curlysister]

There are crabbers who do a slope. However the most shallow end of the slope needs to be at least three times as deep as your largest crab. Once a crab goes under, they often move. And they also don't know to 'choose' the deep end to tunnel and molt. The reason that deep sub is recommended, is so that other crabs don't come across a molting crab while they are vulnerable to being harmed or killed by the other crab(s).

[wodesorel]

This size tank does fit a large terrarium perfectly, the bases on those are 18x36. The problem of course is the cost, as they are ridiculous new and difficult to find used, especially at any kind of good discount. People do get luck though!

I have a 30 breeder that I got with an adoption and I used it vertically for a while, making a screen door to fit it. Ended up having it as a plant terrarium for a bit after that. The size is really awkward and its been in storage for a year. 40 breeders give a smidge more height which is nice. The only wonderful thing about them is they offer a lot of walking space which the crabs will use!

[DragonsFly]

The only wonderful thing about them is they offer a lot of walking space which the crabs will use!

Yes, I've always remembered a comment from you, wodes, years ago, that you like to leave a "runway" for the crabs--a long stretch of tank where they can get up a "head of steam" and really travel. I've done that ever since, always leaving the long front stretch of the tank without obstructions, and doing what I could, as I upsized to bigger and bigger tanks, to give them a clear "race track" all the way around the tank where possible (although it doesn't follow the outside of the tank all the way around), and the "highway" definitely gets used every night!

It is clear that movement is a major key to health for all animals, so anything we can do to allow for and encourage as much movement as possible is a good thing! That's why I put different food sources in different parts of the tank all the time, including up on climbing structures, so they really have to explore to find them; why I have the two water sources at opposite ends of the tank, and why I always keep their "runway" clear.

[EliSH]

So I looked up the terrariums, and wow you are right they are expensive, not impossible, but I am a college student and it will definitely take a while to save up, until then I'll keep an eye on Facebook marketplace just in case, until then, what would you recommend I do? It sounds like it would be better to sacrifice their climbing area for now so they can molt safely (my crabs havent been very into climbing, but will every once in a while to see if I've left food up on their hammock for them). But will they suffer without something to climb if they develop more of a liking to it?

[DragonsFly]

Just keep checking all the online "flea market" type places (craigslist, OfferUp, FreeCycle, I'm sure you can find more). Frequent checking is the key to spotting a good deal before it gets grabbed by somebody else.

In the meantime, movement is important to continuing health, but molting is non-negotiable to their continued survival. Half the tank would be a "footprint" 18 inches by 18 inches, that's pretty "iffy" for 3 crabs, unless they are really tiny. I'd give them more like 2/3 of the tank at 6 inches depth, then maybe slope down to 4 inches (would this still be a good bit deeper than your crabs are tall?).

Get creative about design, so you encourage them to climb even if it isn't climbing very high. You can use hooks on the side of the tank to attach things like a burlap or mesh second level that could be right over a water source, for example, just a few inches over it, and yet allow you to easily unhook that second level to get to the water source for cleaning. The idea is to make climbing structures that do not themselves take up a lot of volume--so, flat mesh fabric levels, the smallest possible cholla, maybe, or split the cholla so you are using basically flat sections of it rather than round ones.

What are you using for water sources? I'd suggest putting them on opposite sides of the tank, as well as putting food sources, mineral supplements, etc., in lots of different places, to encourage maximal movement.