HCA: Hermit Crab Association

TLDR Question: Is there actually a hard and fast best Relative humidity % to go after, or is consistency more important?

Backstory: I've been working on implementing a humidity control system using an Arduino to control it.

My humidity stays around 90-99% (gradient from one side to the other with calibrated gauges) if I shut the lid and do nothing. One particularly cold day in the apartment it actually rained in the crabitat. That was fun to deal with. Also I have a pretty bad mold allergy so I'm trying to combat it and get the humidity down to 80% without me having to prop open the glass lid. I've gone through a few designs and finally settled on using two 1 inch (25mm) fans with one pointed in and one pointed out. I have the setup in place and it works fairly well. I need to optimize the code and add in some more control logic, but for the most part the project has been a success. Once I finish it up and get a box around it I'll post some pics, but for the mean time I had a couple of questions. I have been noticing some interesting behavior trends when the humidity is changing vs when it is constant at any value. This has led me to question whether a target number is important or just consistency.

1. For Purple Pinchers is 80% RH the best target value?
2. Is a target value or consistency more important?

Sent from my moto g power using Tapatalk

80% is the best for purple pinchers. As long as your in the safe range, I think your fine. Humidity in the wild isn’t going to be the same all the time so I would think it would mimic the more natural weather changes.

Hermits are not found in constant high humidity in the wild. That's something the community decided is best, but I personally think it's something that needs questioned and revisited at some point. It depends on species, but reading up on the ecology of PPs and Es, they prefer dry ground, arid scrubland, forests away from the ocean. They carry shells around with water inside to create their own microclimate so they don't need to have humidity all the time to thrive. Studies into their shell water show that they can recharge their reserves in a matter of minutes, but when kept in 80%RH or more they often don't bother to because there is no need for it, so they can adjust on the fly. Given a choice, in scientific studies, they head to dryer areas to hang out instead.

If I'm being honest, I don't even pay attention to the RH anymore. I keep the sub moist, keep their water filled, and let the tank dry out a bit between wettings so there is little to no mold growth. I have horrendous mold allergies!

wodesorel wrote:Hermits are not found in constant high humidity in the wild. That's something the community decided is best, but I personally think it's something that needs questioned and revisited at some point. It depends on species, but reading up on the ecology of PPs and Es, they prefer dry ground, arid scrubland, forests away from the ocean. They carry shells around with water inside to create their own microclimate so they don't need to have humidity all the time to thrive. Studies into their shell water show that they can recharge their reserves in a matter of minutes, but when kept in 80%RH or more they often don't bother to because there is no need for it, so they can adjust on the fly. Given a choice, in scientific studies, they head to dryer areas to hang out instead.

If I'm being honest, I don't even pay attention to the RH anymore. I keep the sub moist, keep their water filled, and let the tank dry out a bit between wettings so there is little to no mold growth. I have horrendous mold allergies!

That's really interesting. Have any readings in mind I could check out?

I'm an engineer, so I tend to make complicated projects out of simple problems just to have some fun with a project. I'm also always interested in scientific research to help with my projects.

Sent from my moto g power using Tapatalk