Real dangers of saturated substrate

[JediMasterThrash]

I always managed to learn something during my deep cleans. That's why I call it "lessons learned during a deep clean". The only problem is that the biggest lessons are usually bad ones. But if the knowledge can benefit the crabbing community, then some good has come out of it.I think we need to rethink how moist we keep our substrates. I know we usually say "sandcastle consistency", which is probably an OK description. But we have to make sure that substrate only stays moist, and never becomes "saturated".What's the difference? If the sand can hold its shape, it's moist. If the sand is wet, it's saturated. EE tends to hold more moisture without becoming saturated, but I think the following guideline will hold for EE as well as sand:-> Keep the top of your substrate dry.This is the top 1/8-1/4 inch. Just the very top. I think that if the very very top remains dry, it means that the lower substrate isn't too saturated with water. If the top of your substrate is too moist, it may mean that the lower substrate has a chance to become very saturated.Ok, lesson was first, now for the information.Here's one of my E's. He survived a recent molt, but as you can see, he has discoloring. It turned out that my substrate was too moist. The lower half, bottom 3 inches were saturated. Your hand got wet holding it. So molting in saturated substrate causes this discoloration. I think the exo has trouble hardening due to the extremely high humidity, and the parts that harden later/slower end up light colored. While the parts that harden sooner are darker colored.This affect can also be seen if you've ever disturbed a recent molter. You'll notice that they never fully darken after being disturbed. I think that they need to harden faster to get the darker color, and when you disturb a molter, it doesn't get to finish hardening right away, and ends up very pale.Now it gets worse from there. As I continued with the deep clean, as mentioned I reached this very saturated sand substrate, and in it were 3 other crabs who had failed a recent molt. And it was very saddening. The sand lining the opening to their shells had completely bricked. It was very bricked. I had to pry the sand bricks off the shell opening with hard objects. The crab behind the brick was super saturated. Like the crab above, but 75% of the exo was lighter areas, and the lighter areas were like puffy with water, and the exo was visibly moist on the surface. The air was just too saturated with water, and the sand was so saturated - there was nowhere for the moisture to escape. The sand was so saturated that the drying at the interface to the drier shell air caused it to brick.How did it get this saturated? If you remember in a previous tank iteration, I was saying how I poured water into the substrate every week to keep the substrate moist and the humidity up. Well, at the time there weren't other factors involved, so it was OK. I had 110w of light in the dry winter so the water evaporated faster. But in the summer it doesn't evaporate as fast. I'd actually stopped adding water this spring, since the substrate didn't seem to be drying anymore.But my waterfall wasn't so cooperative. Well it doesn't help that every time my crabs decide to tip it over, that all the water pumps out into the substrate. This managed to happen many times. I ended up removing the waterfall about a month or 2 ago because I had noticed the substrate was very moist, and didn't want to help it along. That's also part of the reason why I didn't add the waterfall back into my latest iteration.And also I had the substrate up pretty deep/high last time, up near the tops of the water pools. And I think that water was regularly wicking out of the pools into the substrate. It was like I had a leak in the saltwater bowl sometimes. And of course august/july are hot, humid months.It looks like all these saturated deaths were recent, in the past month or two. But from discoloration of a couple very recent successful molters, it looks like the substrate just slowly got more and more saturated over time, until it eventually hit critical mass. I’d noticed a few months ago that the top of the substrate was never drying anymore. It always remained moist on the surface.As I mentioned in my 'tat post, I was 4 months late in doing the deep clean. Surprisingly, the water still seemed OK. There wasn't any bad smell from the water, it was clean. Just too much. If I would have done my deep clean closer to the 6 month timeframe I intended, this wouldn't have happened. But it's good to know that saturated substrate does have a real danger for molting crabs.On top of this, I think we as a community are tending to the extreme on the high humidity side. It used to be 70-75%, then it was 70-80%, and now we hear people talking about their 80-85% humidity and asking if it’s OK, and I generally hear that more humid is better than too dry. I think we need to rethink this. I think that as long as the substrate is moist, and the water bubbles, and the lower part of the atmosphere is above 70% relative humidity it should be OK. But we often have our hygrometers above crab level. Making sure the upper atmosphere stays at 75% may not be that important, as long as the lower atmosphere is high enough. I tend to keep my gauges up out of reach, otherwise the crabs will tear them down and break them.Between my two humidifiers, two bubbling water pools, and moist substrate, I’m not going to be too worried if my gauge half-way up the all only reads 69% this time around. We’ll see what happens. I also have been documented as stating in the past that I think higher air temps can be more important than higher air humidity for crabs. Nothing more than anecdotal evidence though.

[Crabby Abby]

JMT, let me first say I'm very sorry for your losses and thank you for taking the time to share and allow everyone to learn from it.I completely agree from experience as well that high humidity has the potential for more harm than just the increased possibility of causing mold. I too have struggled with wet substrates even after removing my humidifier and not hydrating as often.Large water dishes directly below overhead lights or set against side mounted UTH's also seem to contribute to the problem of overly damp or packed substrate.

[Guest]

Thanks for the information - I was actually about to post a topic about this I'm having issues with saturated substrate in my 10 gallon iso tank. They kept building sand bridges into the water dishes and its pretty soggy now. I'm now using shallower dishes that I don't have to sink into the substrate as much, seeing as the crabs are only teeny. Hopefully this will stop the sand bridges.How can I get the sand to dry out without using a heat lamp? I have a side-mounted UTH on the opposite side as the water dishes. Should I leave the cover off and let the humidity drop for a day? 6 of the 10 crabs are buried, so I'm quite worried about them. -Beth

[Crabby Abby]

Very wet substrate can interfere with hardening of the exo as JMT pointed out (and which is also detailed on info sites like hermit-crabs and TCP) so your molters are likely at risk already of that, substrate collapsing and trapping them or drowning.Can you ID any one area where they are not? If so you can dig out the substrate and use a turkey baster to suck up any standing water or fill the hole with dry sand, or shave a layer off the top (or not,) and gently pour cups of sand evenly across the surface.Bowman whether it's evaporating or substrate is in contact with it and wicking it out, 1-2 bottles daily is much too much water to be adding to your waterfall. Check the underside or wiggle a hole down somewhere into the depth of substrate and see what's going on. You can use a child's toothbrush or coffee stirrer to slowly probe the substrate in a nickle sized radius to the bottom to see if it's safe to make a peek hole there.

[Guest]

JMT, Sorry to hear of the loss of your crabs.I have experienced too wet of substrate when I had my 10 gallon. It was like a swamp at the bottom.Your post has lead me to an idea I have been wanting to ask about.I was talking to a pet shop employee and he was telling me about how to set up a false bottom in an aquarium for tropical species. There is some sort of clay gravel that you put in the bottom of the tank, then cover it with some sort of firm plastic mesh, then put your subtrate on top of that and it works as a drainage area for excess water to collect.In your opinion, would this work or would the substrate be too dry? In addition, molting crabs like to dig all the way to the bottom, how would they react to the plastic mesh?I look forward to your and everyone's opinion of this idea. Thanks in advance.

[JediMasterThrash]

I was actually going to make a post about the terrarium drainage solution I just saw at petco, which is exactly what you described. I think it would be excellent, except that it would cost like 200$ to cover the bottom of my tank, those clay balls are expensive!I haven't really listed specific instructions to perfect a tank. Just some new thoughts and ideas to think about as you care for your own tank.I can see the 6 inches of substrate on the side glass, and I can see the layers of moisture in the substrate. So I can see where the moist and water level is. The top will really only stay dry if there is radiant heat (from overhead lights) and air circulation. Otherwise it will wick up lower moisture. It will probably do that to some degree anyway. But if overhead lights alone aren't keeping the tank dry enough, it could be the air circulation that's lacking. The air becomes saturated with water vapor, and that humid air has to get cycled out in order for more moisture to be expended.Even now there's parts of my tank that are dry, more in the open with the lights shining, and parts that are moist on the top, where the lights don't shine or right by the water bowls. I'm trying to add more air circulation to keep it in check.What is a turkey baster? I keep hearing that used. But I can't imagine a turkey dinner having anything to do with syphoning water.The sand below the surface stays moist. New sand is always moist, so the substrate always begins at sandcastle moist. I actually used a hair drier while I was pouring the new sand to dry it a little bit, so it wasn't too moist. After that, to add moisture, make a hole into the corner of the substrate and pour water down the hole. Then the water will soak into the lower substrate, where it will spread out through the whole whole tank and hold the moisture longer. Misting only gets the surface wet, and it will evaporate completely within the hour.

[JediMasterThrash]

Crabs tend to use edges of things (walls, dishes, toys) as the starting point for digging down. That's why I suggested keeping the dishes out of the corners, because corners are favorite places to begin digging down.However, once the crab is down, they tunnel all over the place. If a crab remains in a corner or along the wall, you can see their little "Crab window" as I call it. However, I haven't ever yet had a crab molt along a wall. So far they've always been more in the center of the substrate when molting. Though it would be nice if they would molt in a crab window, so I could get some cool pictures.If you can't see the crab window, there likely isn't a crab right there, and it would be safe to finger a hole.When you fill the hole with water, it initially looks saturated, but it quickly seeps into the surround sand and eventually spreads evenly through the entire lower substrate. Also, by using the hole, the water has a direct path to the bottom, so it starts wicking up from the bottom, rather than being poured down ontop of crabs.If a crab gets extra moisture for a few hours until the water finishes distributing around the entire tank, it shouldn't affect them. Crabs molt with their shells face down, so water wouldn't enter their shell and drown them.Now, the real point would be to make sure that you don't add so much water so as to fully saturate the lower substrate. If you add too much, it could easily end up with soggy substrate like I had.Usually that isn't as much of a problem in my 10g ISO, because the sand is only 3inches deep or so (I don't usually get big guys to ISO, but I add more sand if needed), and with the moonglo and propped lid, and no bubblers or humidifiers, the humidity quickly evaporates, so the moisture continues to evaporate from the substrate fast enough that it doesn't get saturated.Also, I have a UTH on half of the bottom, and the substrate over the UTH tends to dry out really fast, so usually only the other half stays moist. In fact, pouring water onto the UTH side causes it to evaporate faster keeping the humidity up more.But your point is valid. You have to take into consideration the properties of your particular tank to know how much water to add and where to add it.One idea to prevent having to refinger holes would be to use some plastic tubing and place it into the corners, and then you could just add water into the tubes, and it would come out the ends which are on the bottom.