HCA: Hermit Crab Association

So I bought everything that was recommended. Found out my sand was dangerous. Will be putting new playground sand in Saturday. I mixed sand/substrate together first time around. Second time I put coconut substrate down first, then sand. Then I read about mixing. What is the order please? Thank you.

Most crab owners (including me) have 5:1, playsand to cocofiber, substrate that is mixed together.

When I was mixing mine, I found that the easiest way to do it was to find a scoop (mine was about a liter), then do 5 scoops of sand, 1 scoop of cocofiber, and mix. Then repeat however many times you need to get up to 6+ inches deep. Don't try to use a spoon/tool to stir, you really need to use your hands. Make sure when you're mixing it together that it is at sandcastle consistency.

If your cocofiber comes in a brick, you will want to reconstitute it (per the package instructions) with dechlorinated water before adding to the tank. If it comes in a bag, you can use it as-is.

Thank you very much. You were very helpful. I’m changing out today. Trying my best to make these guys happy !

Alyw77 wrote:So I bought everything that was recommended. Found out my sand was dangerous. Will be putting new playground sand in Saturday. I mixed sand/substrate together first time around. Second time I put coconut substrate down first, then sand. Then I read about mixing. What is the order please? Thank you.

I do one brick of eco earth for 100 pounds (give it take) of playsand… I try to dry the eco earth out as much as I can before mixing.


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There is no right or wrong way of having cocofiber and playsand. You can mix it, or not mix it. Use just cocofiber, or just sand. The only important thing is that it's been moistened enough so that it holds its shape when squeezed, so the crabs can tunnel and make molting caves. Personally, I've use straight sand for over a decade because of allergies, but having some cocofiber can help with steadying humidity levels a bit more.

I have an under tank heater. One on the side. And I just added one on the back. I have a dual hydrometer/thermometer in the tank. The new heater attached to the back is set at 83 degrees. I have a saltwater dish, a fresh water dish, sponges, no I just bought moss. The temperature is reading about 55. The hydrometer is low. However there is condensation all over the tank. I can’t see inside. It’s definitely humid enough. I have a mesh top that I covered with press and seal wrap from the grocery store. Why isn’t it warm enough or humid enough according to the inside hydrometer/thermometer? I don’t know what else I can do for heat?

Alyw77 wrote:I have an under tank heater. One on the side. And I just added one on the back. I have a dual hydrometer/thermometer in the tank. The new heater attached to the back is set at 83 degrees. I have a saltwater dish, a fresh water dish, sponges, no I just bought moss. The temperature is reading about 55. The hydrometer is low. However there is condensation all over the tank. I can’t see inside. It’s definitely humid enough. I have a mesh top that I covered with press and seal wrap from the grocery store. Why isn’t it warm enough or humid enough according to the inside hydrometer/thermometer? I don’t know what else I can do for heat?

Cheap ones can be really inaccurate


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Ok. I’ll get a better one. Thanks.

I had one for months that was 8 degrees lower than the real temp and had no idea


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Is your thermometer/ hygrometer digital or analogue? The analog tend to be less accurate than digital. Many of us use Accurite brand, they aren't expensive at all (I got the last one for $8 Canadian on sale).
Over in the files section, there is a care sheet that outlines how to calibrate a hygrometer to see if it is accurate. That will tell you if the reading is true or not.
As for the temperature, what temp is the room where the tank is? Condensation on the glass is from a temp difference inside vs outside the tank. I am doubting that your room temp is 55, so for sure the tank would be warmer than that? If you take the thermometer out of the tank, what does it read?

My thermostat is set at 71. The thermostat is analog. I just bought another heating pad and the digital read is about 83. The hydrometer went up this morning. I ordered a digital hydrometer/thermometer for inside the tank. The thermostat was out of the tank and it was in the 70s. By the way…. One of my hermit crabs just buried a little in the sand on the warmer side of the tank. One has buried under the substrate a while ago. The third has been in the surface but just sitting there. Is it too warm/humid? Humidity is about 75. Temp in the tank reads 70. A huge amount of condensation on the tank.

There is no 'too humid' - so anything over 75 is good for humidity.
Temperature should be over 72F in the tank for PPs, anything lower gets into a dangerous zone that crabs are not able to survive in. Having the temp closer to 80 will make the crabs more active. It should not be routinely over 90, as that is too hot.
Condensation on the inside of the glass only means that there is a difference in temp between the tank and the room.

Ok. Thanks! Very good to know about the tank temp & humidity. That’s about what I do. The tank feels warm and humid when I open it.