HCA: Hermit Crab Association

I am having difficulty keeping the humidity and substrate moisture at a constant level. I have an acrylic lid that brings the humidity up to 99% when I put it on, but the substrate dries up to the point where my crabs can't dig. Any suggestions on how I can keep the substrate moist but keep the humidity level below 85%?


And also how can I post a photo from my camera roll without using social media?

A cheap way to create constant, steady way to create humidity, and I'd say the most popular method recommended here is using a small aquarium pump, tubing and airstones. I purchased all these items for around 12 to 15 bucks at Wal-Mart. You can use the pump and airstones, and it essentially creates an in tank humidifier. I turn mine off if I notice it spiking too high, like above 90. High humidity won't hurt a crab, it just makes mold more prone to grow. Also, have you calibrated your hygrometeter recently? The very top of ny substrate does get dry along where the UTH ends, but only the very top, and I mist the tank there about once a week and it's fine. Having a high humidity should prevent it from drying out too much though. Submitting a pic of your tank would definitely help us help you.
As far as I know, the only way to share pics without a hosting site such as tinypic or Photobucket is by using the mobile app tapatalk, it has a feature that inserts pictures for you.


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I am pretty sure it is because of my heat lamp. I cleaned the tank yesterday and moistened the substrate to a moist consistency. Today The top few inches were already dry. The crabs are in a 20 gallon terrarium and I have a 150w heat lamp. I have tried placing the lamp further away from the tank but it doesn't help. Any suggestions on how I what type of lamp I should get or how I can fix this? I will get tap talk and try to post photos soon.

And I already have an air pump to keep humidity

Heat lamps are sadly notorious for sapping humidity. I would suggest switching methods of heating to a UTH across the back of your tank. Many, including myself, get the Ultratherm brand from reptilebasics.com. or the bean farm. We usually recommend the largest that fits across the back of your tank, but slightly above the substrate line, to heat the air. This brand is removable, runs hotter, and uses less electricity than most pet store brands. Meanwhile, maybe try a shallow dish for water with a large surface area right under the lamp, hopefully it evaporating will help meanwhile.. others use damp towels on top of the tank, but with a lamp, I'm just not sure how it'd work.

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I always use lamps for my main heat source; if they are not too close to the substrate, I don't have any problem with drying out. How big is your tank?

To keep the humidity from spiking too high (and improve overall well-being, and help deter mold) a small fan in the tank helps keep air moving and may prevent the water vapor from all condensing on the tank walls (which must be what is happening if you have a solid lid, the moisture is evaporating from your substrate, but humidity still reading high in the tank?).

Not too terribly experienced here, but 150w seems to be way too much.

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Sorry, I didn't see that information posted. Yes, for a 20g, I'd say you don't need 150 w to keep temps in the 75 to 85 degrees F range. And when you say you have an "air pump," do you mean a humidifier-type apparatus? Bubble pools are much better at increasing humidity than humidifiers, plus vastly easier to keep clean, and they keep your water sources fresher longer. I'd put a lower-wattage night bulb in your heat lamp and install bubble pools (all you need is the air pump you already have, enough air tubing, and a T-connector ("splitter") to make both of your water sources into bubble pools. Putting the air pump on a timer allows you to adjust how much it is on or off, to fine-tune humidity levels. Best wishes!

150 watts for a 20 gallon is overkill. I myself use a 60 watt day bulb and a 100 watt red heat light for night time and my main tank is a 70 gallon tall.

I use a 40w for a 20L as supplemental heat to a Zoomed UTH. I would think that a 150w would melt the trim on the tank or you would have to set it so far away that most of the heat would be lost to dissipation.

Can you drill a few holes in your Plexiglas Lid? That would allow the moisture to vent and give you some fresh air circulation as well. Just a thought.

If the substrate is drying out, you don't want to vent the moisture; you want to adjust the heat sources so they don't heat up the substrate to so high a temp that the moisture bakes out of it.

It really is a steep learning curve of trial and error, getting a tank balanced for temperature and humidity. The good news is that, once you do so (assuming nice deep substrate at proper "sand-castle" moisture), the tank will want to maintain both temp and humidity (it has to do with the "thermal mass" of all that warm moist substrate). This does take time, to get the substrate to proper temp (unless you are smarter than I was and warm the water you use to dampen the substrate ahead of time), but once your substrate is both warm and moist, it becomes your ally in maintaining both temp and humidity in the tank.

I would definitely ramp down the wattage of your lamp and see how much that helps. It might solve the entire problem. Make sure you have both temp and (calibrated) humidity gauges in several places in the tank (putting them on popsicle sticks or chopsticks, rather than sticking them to the tank walls, allows greater flexibility and better placement for readings of conditions where the crabs actually spend time).