HCA: Hermit Crab Association

Hello! I am not yet a crab owner, but will be looking to get some crabs in the near future. I have been doing tons of research beforehand to make sure I do everything correctly.

While so far I think I have a pretty good grasp on what will and won't work in my tank setup, there is one thing I haven't gotten a straight answer to.

I really want to make a super beautiful tank that fits my apartment decor as the hermies will be in my living room. Most of my furniture is black, and I wanted to make a tank that somewhat "matches" that aesthetic. For my substrate I really want to use a black sand. I found some black flourite aquarium sand on Amazon that looked like it might work, and also found some other options on Etsy, they seem to be made from silica which I was under the impression was okay for the crabs (I have read about humans having issues inhaling the dust, but that seems to be mostly towards factory workers who are inhaling constantly).

I also plan to mix my substrate with coconut fiber, so I know it won't be 100% black, but I just like the look of a dark substrate in the tank. I also plan on using black lava rocks for the crabs to climb on (which I also read was fine, but correct me if I'm mistaken). I was wondering if anyone here had experience using dark or black substrate? From what I have read, it seems like it would be okay as long as it packs well and is free from harmful metals and things of the like. I do plan on thoroughly rinsing (and potentially boiling) any sand I purchase beforehand.

Obviously if experienced crabbers tell me that's a no-go, I will forsake aesthetic for my crabs comfort and health, but I would love any input!

True silica based black sand has become extremely hard to find lately. I wanted some for a fishtank and the only legitimate stuff I could find was $$$ from petco. (Diamond Black.) There were problems with the caribsea brand of black moonsand a few years ago where it was contaminated and it was pulled from the market, so aquarists have been cautious ever since.

Fluorite sand is not silica. It's a porous clay made for aquarium plants so that fertilizers can reach the root systems. I've never seen anyone use it for crabs and I doubt it would create a healthy crabitat.

Other black sands are usually a form of sandblasting sand, which are no longer natural silica sand due to health regulations but instead are made of coal slag. This is where things get iffy. Have aquarists used this stuff safely for a long time? Yes. Are there multiple reports of metal contamination and tank die offs? Also yes. It's not regulated for animal use so there's no guarantees that every bag will end up being safe enough to use. In theory if it's safe for aquarium use it should be okay for the crabs to be around, but again I've never seen anyone use it before so they could potentially have issues molting in it.

while it would not 'fix' the problem of the interior view.. you could put black around the bottom of the tank where the substrate is, so that as you look from the outside.. you don't see the bottom substrate portion through the glass.. you'd only have the 'top' view to contend with..

just a suggestion

Lost renovating my hermit crabs tank today. I found a bottle of black sand that I’ve got from vacation, I decided to put it in their tank to cover one of their cavelike things. I know that black sand might be formed from lava and have metallic ions in it. I know metal is very bad for hermit crabs, so is this bad? Is this black sand bad for the hermit crab?