How can I keep deep substrate sufficiently moist?

Questions about designing a terrarium.
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Jae Senji
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How can I keep deep substrate sufficiently moist?

Post by Jae Senji »

jae senji hermit crab terrarium 01.JPG
jae senji hermit crab terrarium 02.JPG
Hello all! I have 3 golf-ball sized hermies in a 36x12x25in (WxDxH) tall tank. My substrate has 6 inches of depth on one side, then slopes down to a 2in section where my salt water pond rests. The substrate is a 5to1 blend of Quikrete playsand and EcoEarth, the seemingly most common online hermie substrate recommendation. It was made to be sandcastle consistency when I placed it in there.

I was wondering how folks with elaborately-arranged (i.e., difficult to dismantle) terrariums, with a similar substrate mix and depth, are keeping their substrate moist (sandcastle consistency) all the way through to the bottom. The only recommendations I could find were to frequently spray the surface, or to periodically re-blend water into the substrate which would require dismantling and removing most of, if not your entire setup, and then having to reset it once finished.

Although spraying seems to most often just be a suggestion for increasing humidity (which is not an issue in my tank, even if I spray infrequently), it has also been presented as a way of keeping the substrate adequately moist for digging and tunneling. It seems that would be enough if your substrate was only 2 or 3 inches deep, but at a depth of 6in, no matter how much I spray, when I stick my finger all the way into the sand, the hole just fills right back in with dry sand - the surface wetness from spraying does NOT make its way down into the depths of the substrate.

Obviously, completely remixing the sand with water periodically would do the trick. But not long after placing my moistened mix in the tank upon first setting it all up, it dried out very quickly despite the humidity always being perfect. So, it seems like a complete re-blend would have to occur fairly frequently to keep it at that desired consistency. But, like with my setup, I can't imagine some of these very elaborately arranged terrariums that can be seen online, some of which are much more involved than mine is, being dismantled very often to do this. I can see how with a setup like this, for example...
hermit crab patch.png
...all of the landscaping could be easily removed for a quick, thorough re-moistening of the substrate, and then all of the objects easily replaced. But for something like this...
sugarselections.png
...it seems very unlikely that the tank is dismantled very often for a complete re-wetting of the substrate. Then again, that tank's substrate is 100% coconut fiber like EE which may hold enough moisture to remain "diggable" indefinitely simply from the humidity in the tank and/or just by occasional surface spraying (I have no experience with using 100% EE).

I've seen some enthusiasts stating that it doesn't matter at all how dry the substrate is because the crabs will make it as wet as they need it using water from the water dishes/bowls in the tank. I know this to be true from my first hermie tank (this is my second), the one my 3 hermies began in when they were tiny. But that tank was much smaller and only had a couple inches of a much finer all-sand substrate. So, it seemed to be much easier for me and the crabs themselves to keep the sand adequately moist for keeping it suspended in the "shape" they needed for molting. I hadn't done near as much research before beginning that tank, so I was using the made-for-hermies, box-store calci-sand that everyone forbids. In spite of its negative reviews, though, those hermies molted multiple times and grew much bigger using that sand with no issues whatsoever (just an interesting side note). Will the crabs' own method of wetting as they tunnel be sufficient enough with this type/depth of substrate to keep their burrows from collapsing on them especially while they're molting?

Might it simply be that the so-often-recommneded 5to1 playsand-EE blend, or even 100% playsand, is not the best substrate choice if you want it to fairly effortlessly remain moist throughout, have significant depth, but want to avoid having to dismantle your landscaping (or at least not very often)? Should I use a finer sand (playsand seems somewhat course, and therefore, maybe too easily aerated) or a blend with more EE than 5to1? Or is there simply some "technique" I'm not thinking of to get the moisture needed deep into my substrate to ensure safe tunneling for my crabs without the worry of collapse? Or do I have to just bite the bullet and dismantle my entire tank periodically to access the substrate below to re-blend water into it?

Thanks in advance for any advice you can give me!!!
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emmac350
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Re: How can I keep deep substrate sufficiently moist?

Post by emmac350 »

I never did a full dismantle to re-wet the substrate. Instead, I'd just pour out the fresh/salt water on spots that appeared dry when I changed them out. If I was topping off their water bowls (I'd use the reservoir from a spray bottle), whatever was left in the reservoir after their bowls were filled would do the same.

This was with a 100% EE tank, but the principles apply. The crabs would sometimes empty out their water overnight, presumably by using it to wet other areas of the tank, or because they dug substrate into their water. I'd just dump that out in places that were harder to get water on and call it good.

Have you actually had issues with the tank substrate drying out? Or is this a 'what if' sort of question? The biggest area that I had trouble with maintaining dampness was right in front of the under tank heater (on the side of the tank). Adding water there also helped the humidity, since the heater would cause the water to evaporate.

I think you'll be surprised with how little you need to do a large re-wet the substrate if you do like I mentioned above. My upper levels would dry out the most, so 95% of the time I was re-wetting I would just wet those.
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Re: How can I keep deep substrate sufficiently moist?

Post by aussieJJDude »

Welcome to the forums! I hope you like it here :)

Is the entire substrate dried out, or just the top layer?? If the top layer, how much?
Believe it or not, but having more substrate is easier to control humidity and in turn, control substrate wetness! So you might want to think about adding some more substrate to the 2 inch side, plus if a hermit crab moults there, there is a high chance that another might find it - next thing you know, bye-bye hermie!
For me, it does look like that it doesn't have the 5:1 mix, normally I see a lot more EE in there. But never mind, any mix should go dry! :) Maybe just recommend the 5:1 ratio as it closely mimic there habitat in the wild. But there has been a number of people that kept straight EE or straight sand without moisture problems in there crabitat.
Also, what do you use to heat the tank - if no, just ignore this paragraph? If you were using a UTH (a reptile heating pad also known as under the tank heater) and placing it under the tank, then that is the reason why the substrate is dry. Placing it on the side is better as you want to heat the air in the tank, not the substrate.
It is ok to have a bit of the substrate dry in the tank. I do near my UTH and it is one of there favourite hang out areas! however to moult, my guys do prefer the wetter substrate...
BTW, you had a fantastic tank and if I showed my guys your tank, they would be packing there bags and moving to the US! :) Your clan is very lucky to live in a 5 star hotel!
(Sorry about the information overload, if you read all of it good job and I hope I been a help)
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Jae Senji
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Re: How can I keep deep substrate sufficiently moist?

Post by Jae Senji »

emmac350: Funny you should mention pouring your water dishes out onto the dry spots. I was wondering if it would be ok to pour a little water directly onto the substrate to really get some water down into it a little further than the mist of a spray bottle. Sounds like that's ok, from what you're describing (as long as it's not TOO much water, I assume).

This wasn't a "what if", but I did just set up the tank fairly recently. So, now I'm starting to think that I simply did not work enough water into the substrate from the start. I just sprayed it heavily with salt water in a spray bottle as I was blending the sand and EE together. Once I got it to the point where I could make it hold shapes, I stopped spraying coz I was a little nervous about getting it too wet. It seems I may have been a bit too conservative and just got it to the driest end of the sandcastle-consistency spectrum (if that makes any sense), but could/should have made it significantly wetter by adding the water more heavily (without making it dripping, of course). This brings me to another question: what is the best way to work the water into the substrate (specifically with sand or mostly-sand mixes - seems with 100% EE, you just soak it and ring it out) when it is being newly prepared? Do you just pour it in incrementally, blend, and repeat until the consistency is right? Or do most folks use a spray bottle as they blend, like I did?

Concerning heaters, since I just set it up, and it's the summer here in San Diego, and I don't have AC, the only heat source needed right now (and only at night) is this heat lamp (with a 100W reptile moonlight bulb) I place to one side at the front of the tank as seen here...
jae senji hermit crab terrarium 03.jpg
Once it starts to get cooler, I'll be adding a couple large UTH's to the sides just above the substrate. So no, I don't think heat sources are the issue coz I don't really have much of that in place yet. Again, I'm starting to think I simply didn't wet it enough from the start. I'll most likely just pull everything out of there and redo the substrate. Thanks a lot for the help!
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Re: How can I keep deep substrate sufficiently moist?

Post by Jae Senji »

aussieJJDude: Thanks a lot for the response and the welcome! The substrate seems to be dry throughout. I responded to most of the questions you and emmac350 had for me in my reply to emmac350, so please read through that, if you get a chance, and let me know if you have any additional thoughts. But you brought up some additional points for consideration. If I redo my substrate, I will consider adding a little more EE (I measured what I did, so it should be at least close to 5to1, but who knows), and making the substrate the same depth all the way across.

BTW, if you took the time to make it all the way through MY monstrous initial post, the least I could do was read your entire response! ;) It looks like you're just as wordy as I am! :D
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Re: How can I keep deep substrate sufficiently moist?

Post by emmac350 »

Jae Senji - the trick is to pour a little but not a lot. Especially if you have crabs dug in, pouring a lot of water onto the substrate *could* collapse their burrow. If they're mid-molt or immediately post-molt, that could kill them. I had smaller water bowls size-wise compared to some (Pyrex custard bowls) so I never felt like it would be a problem (nor was it, in my case). But if you're careful to just sort of drizzle the water over the drier looking spots, you should be fine. Every few weeks/months I would scrunch the water into the top layer of substrate. My sub is fairly even tank-wide around 6-8" of pure EE, so I'd just scrunch it about finger-deep (as deep as my fingers went). This was also nice to find buried shells and tank ornaments.

I can't imagine this would be a problem with your sand/EE mix though. So maybe it's worth a shot? You shouldn't need to tear EVERYTHING down. If you can work the water into the easier-to-get-to places, capillary action between the grains of sand/EE will help the places you didn't work it into to take some of that water from the wetter areas. I also think that crabs will be smart enough to bury in the places that are as wet as they prefer, since the ground isn't uniformly dry outside.

TL;DR: wet the areas you can, the crabs should be just fine. It's really hard to see pooled water on the bottom, so you might think it's too dry when really they're under the sea at the bottom (I know, because I did that with one of my first tanks...).
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Re: How can I keep deep substrate sufficiently moist?

Post by Jae Senji »

emmac350: Cool - thanx! Maybe I'll try that first before redoing the whole thing. Going off on a bit of a tangent here, have you had a 100% good experience with using nothing but EE as your substrate? No issues with the crabs' tunneling or with pests or anything else? Have you ever tried just sand or a sand/EE mix in the past? Just curious since you seem to be an enthusiast, yet it seems like the majority of enthusiasts out there recommend the 5to1 thing. If I did end up reworking my substrate, I was considering going all EE or even trying a 1to1 (half-n-half) sand/EE mix. What seems best to you personally?
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Re: How can I keep deep substrate sufficiently moist?

Post by emmac350 »

I used to be 100% sand, then I was sand for the main tank and coco fiber in the upper levels, then I went with all coco fiber. The reason for that was that my crabs seemed to vastly prefer the coco fiber in the upper levels. They molted in 1.5" deep coco fiber, and none of the coco fiber molts resulted in the crabs dying whereas I had several in sand that did. This isn't scientific evidence, but that's why I switched. Now that I have switched, I love it because I don't feel guilty throwing it out during tank change/deep clean. It's biodegradable, and then I don't clog my sink trying to rinse sand or lug around heavy things of sand to rinse/bake/repeat.

I like the look of the all EE better, it holds humidity amazingly, and my crabs seem to like it. I expand it with salt water, which would kill any pests in it (mine is in the compressed bricks; if yours is loose, soak it in salt water and you should have the same result).

If you're mildly OCD/neat freak, trying to have sand in some areas and coco fiber in others will possibly bug you...the crabs will absolutely mix them up. I spent more time trying to pick sand out of the EE and EE out of the sand...yeah. Your crabs might appreciate having a choice in where they live, and they very possibly might give you pretty clear feedback about which they prefer (like mine did). My crabs hated playsand, though, and only tolerated aquarium sand. Maybe it was too scratchy for them? Not sure. But they love (and even eat) the EE.
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Re: How can I keep deep substrate sufficiently moist?

Post by aussieJJDude »

Jae Senji wrote:aussieJJDude: Thanks a lot for the response and the welcome! The substrate seems to be dry throughout. I responded to most of the questions you and emmac350 had for me in my reply to emmac350, so please read through that, if you get a chance, and let me know if you have any additional thoughts. But you brought up some additional points for consideration. If I redo my substrate, I will consider adding a little more EE (I measured what I did, so it should be at least close to 5to1, but who knows), and making the substrate the same depth all the way across.

BTW, if you took the time to make it all the way through MY monstrous initial post, the least I could do was read your entire response! ;) It looks like you're just as wordy as I am! :D
Welcome!
Since it is dry throughout most likely you were holding off on the water at the start! Don't worry, I did the opposite and had to make my first moulter do a surface moult! Wasn't fun at all! :(
When having more EE, I notices that my substrate says at a better sandcastle consistency for longer, plus does wonders on the humidity! I don't think you would have to take everything out, maybe just a gallon of water is poured in the corners will do the trick, and would disrupt the crabs compared to taking everything out... However taking everything out does have it advantages like add some new toys for the crabs. ;)
Don't worry, I did look through your informative post - which is good, that way there is less questions we have to ask to help you and in turn, faster response! Lets just say that English isn't my strong point, but believe me, I did have a couple of reads through your post! XD
246L/65G - 'Tidal Jungle' (Crabs) | 246L/65g - 'Backwater Pool' (Fish/Snails) | 96L/25G - ''Twisted Minds" (Fish/Snails/Shrimp) | 300L/90G Fancy Pond (Goldfish)

I've never had any problems with 'Impulse Buying'. They're just animals that I forgot I had planned to get.
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