Red Claw Crabs

I think critters add a lot of character to a tank, and they do some pretty interesting things, too—that is, besides just swim around. I asked around quite a bit and got a whole bunch of advice. In today’s blog, I will talk about one of my favorite critters, red claw crabs.

This isn't the best photo. They are very well camouflaged, and are hard to photograph.

I saw a tank full of these guys at Pet Smart, and bought the biggest one—a lively female. The clerk mentioned offhand that they were semi-aquatic. I figured, yeah, whatever. I’ll just take it home and if there’s a problem, I’ll think of something.

I just love crabs. I love the way they scoot and skitter around sideways on their long, spidery legs. I like the way their eyes are perched at the end of long spindly eye-stalks. I like their massive claws. There is something mechanical about crabs in the way they move and eat.

So, how do you tell if you have a male crab or a female crab? Well, you turn it over (which requires you to hold the little guy with a delicate but firm grip—not easy to do), and look at the under-side. There is a flap attached to what appears to be the crab’s butt, which curls under the body and runs back toward the mouth. This flap is called the abdomen, and yes, it does contain the intestinal tract. On males, the abdomen is very thin, like a pencil. On females, the flap is very wide, sometimes rounded and sometimes triangular, but it is distinctly wider than a male’s.

Well, I put the little gal in my 20 gallon tank, and had fun watching her explore, looking for a place to hide. In the same tank I also had an African dwarf frog. I am not sure if putting the two together was the best idea. I came downstairs a few hours later and found a neat, frog-shaped skeleton lying on the gravel. Mmmmm, someone had a tasty meal!


I know this photo looks suspicious, but in fairness, I had just recently moved the frog into the 20 gallon tank, so it might have died from the stress. Regardless, I would think twice about pairing the two in the future. A quick check on the web reveals that their habits are similar to cray-fish. They are omnivorous—i.e., they eat everything, and they’re not even slightly picky. Don’t mix them with any kind of fish that lives on the bottom.

Red claw crabs like to hide, so if you want to see them regularly, you have two options: buy a bunch (so that there is always one out doing stuff), or don’t put anything in the tank for them to hide under.

Here is a hard, fast rule for any aquarium animal: “If you give them a place to hide, they will”. If you want to actually SEE your critters, don’t give them a place to hide. Nevertheless, all animals need some place to hide from bullies and more aggressive species. There is a fine balance.

These little guys LOVE TO CLIMB. They WILL FIND ANY OPENING in your tank. They can shinny up any hose or tubing that goes from the bottom to the surface of your tank. My crab escaped after just a few days. I was afraid she had gotten out, but eventually I found her hiding under the bio-wheel filter. Be warned, crabs can climb! I sealed off every opening of the tank with half-inch galvanized mesh, and haven’t had any problems since.

Red claw crabs are semi terrestrial. They like to come up for air a lot, so you need a decoration of some sort that protrudes above the surface. I made a platform of wood, 2x3 inches (just a small piece of plank), and attached a long strip of galvanized mesh for a ladder. Now the little gal has safe, easy access to the surface, and she can’t get out. She spends lots of time up there. I attached the bottom of a can so she has something to hide under.

Here is a link I found on the web. Apparently red claw crabs do better if you add a pinch of salt. This is a website of a pet shop. They have lots of interesting info.

http://www.aqualandpetsplus.com/Bug,%20Red%20Claw%20Crab.htm