I currently have a 55 gallon fish tank up and running, and needed my 10 gallon fish tank that held my fiddler crabs for something else. Being that fiddler crabs cannot completely live under water and actually need to out of the water, i was left with an issue, the solution, make a dry zone for them. I have seen a bunch of them for sale, but what is the fun of buying something when you can make it yourself :D
quick list of what you need:
1. clear jar large enough for a couple of fiddler crabs to crawl into
2. Aquarium fish tank air hose
3. Aquarium air pump rated for your tank
4. aquarium air stone
6. (optional) decorations for inside the dry zone
Step 1: Get a Jar
First, get a large clear jar, being that I have a 55 gallon tank, I have enough room for a large "Mt. Olive" pickle jar, luckally for me, my wife likes pickles, I had an empty jar kicking around. Clean out the jar, if you must use soap, really rinse out the jar, while at it, try to peel off the labels.
Step 2: Weigh Down the Jar and Fill With Air
Now that you have a nice clean clear jar, need a way to keep it on the ground. With my set up, I had to put a rock under the back of the jar, filling it half full of sand/aquarium rocks. Being that fiddler crabs prefer sand over gravel, I filled my jar with sand. Clear out the area that you are going to lay the jar in. Keeping the mouth of the jar facing up, slowly submerge it into the water until you the jar reaches bottom. Slowly tilt the mouth of the jar towards the center of the tank and pile up some sand/gravel at the mouth of the jar to keep it from sliding forward, making sure that the bottom of the jar is at an upward angle. Next pop the air stone on the end of the air tube that you are going to be putting into the jar, and feed the hose into the jar, if you want to, you can cover the hose with the gravel/sand. Attach the other end of the hose to your air pump, if you have one, I would suggest an air regulator to adjust how fast the air fills the jar. The first time I set mine up, I didn't have enough weight and the jar popped off the bottom of the tank. Just add more sand until your jar stays at the bottom.
I happened to have a few sponge bob figures and thought it would be funny to have sandy cheeks standing in my dry zone.
Now i have seen a few things that say occasionally turn the air on blah blah blah. I have had my air supply feeding into this non-stop since i first set it up, and the crabs ignore the bubbles escaping the mouth of the jar and chill out there for a while.
As a warning, if you are going to use sand, be prepared to not be able to see inside your tank for a while, sadly because all my sponge bob stuff was in my 10 gallon set up, and I was lazy just scooping the sand and dumping it into my 55 gal set up, I have lost patrick under all the sand, eventually he will show up when the shark decides to move the sand to his liking :D