"This stuff is AWESOME! It holds humidity extremely well, which is crucial for hermit crab husbandry. It also is great for the crabs to dig in and bury themselves -- a MUST for safe and proper molting. It is vastly better than any other substrate -- aquarium gravel, sand, bark, mulch, crushed coral -- that I have used before. The hermies LOVE it!
The stuff expands to make a lot of substrate, Two bricks was enough to give 3-4 inches of substrate in my 20-gallon long. It doesn't take long to make and is easy to store when not in use, thanks to the brick compression. Once in the tank, the dark brown color is very attractive and gives a sharp contrast with the crabs and their various toys and tank decorations. It looks really good.
My only very minor "complaints" are as follows: The stuff is quite messy. The crabs trail bits and pieces of coconut husk into their food and water bowls. Also, the aroma is not particuarly pleasant. I wouldn't go so far as to call it frankly offensive, but I'm glad that the tank is largely covered by clear plastic to keep the humidity in the tank (and hence the aroma as well).
Lastly, you really can't clean the stuff by simply rinsing and washing it -- at least not like you can with crushed coral and gravel. You need to throw out all the substrate and replace it de novo. That is, unless you are willing to comb through it and manually remove all the decapod waste. With gravel and crushed coral, I would just wash the stuff out and reuse it. On the flip side, this product is infinitely better for satisfying the digging and burrowing needs of my hermies.
Overall this is a FABULOUS product for hermit crabs. It is reasonably priced and lasts a long time -- with a month or more, even up to 3 months if you do "spot cleaning", between changes -- so the inability to wash it and reuse it is not a big deal. I will most definitely keep getting it."