A Pithy Ally In The Fight Against Algae!

Today we're going to introduce you to the crab you've never heard of but should have. So, without further ado, let us present to you, Pitho mirabilis. We'd rename it the Miracle Crab, but alas, everyone already calls it Pitho Crab. They stay relatively small, are super peaceful, are decorators (more on this later) and will eat just about any kind of algae you have in your tank, including the notorious bubble algae.

The wild home for these crabs is the Caribbean and small section of Atlantic coast. There they live in pretty shallow water, in tidal flats, seagrass beds and reefs, basically anywhere there is enough sun to grow the algae they live on. The females look quite a bit like the more famous Emerald Crabs, including the over-sized claws, though the carapace (big shell part) is slightly more Decorator Crab in appearance (pointy in the face, rounded in the butt). The males look pretty much the same but are generally a tad smaller and lack the big burly claws. The similarity to Decorator Crabs doesn't end with their shell shape. The Pitho Crab will also decorate its shell with bits of whatever it finds; algae, sand, small rocks, even sponges and polyps can end up there. When undecorated they are usually off-white, to pale yellow in color, though tan-brownish specimens aren't uncommon either, looking a lot like the sand they'll like to hide in if you have it.

The similarity to Emerald Crabs is more than an aesthetic. Like the Emerald Crab, Pitho Crabs will also consume bubble algae though there is a difference; Pitho Crabs do it much better. When it often seems like a crab-shoot as to whether or not an Emerald Crab will eat the insidious bubbly green growth, Pithos will pretty much always eat it, we've seen very few individuals who didn't seem to prefer it. They don't stop there either, they love hair algae and a variety of caulerpa, brown and turf algae too.

They're so good at eating algae that they're probably going to run out and you'll need to supplement their diet. Here we rely on Nutramar Ogo and Nutramar Nori to get them nutrition when we don't have any live algae to feed them. They'll also happily pick away at the Nutramar Algae and Color Boost Shots (which most of your fish will love too, especially your grazers.) Just tuck a bunch under a small rock on the bottom of the aquarium.  You could also farm algae for them by growing it in a refugium or even a dedicated tank set up to grow the stuff. Just leave rocks in a saltwater tank in the sun, and they'll start growing plenty of algae in no time. You can move those rocks to the main display until they are clean and then send them back to the farm to regrow more food (again, your Tangs, Rabbitfish and Lawnmower Blennies will love this too!) Pithos Crabs are nocturnal in the wild and will spend most of their day partially buried in the sand, usually with just their decorated hats sticking out. Over time, they'll become much more accustomed to being active during daylight hours. When you first introduce them, and if you have very little algae in the aquarium, do your feeding after lights out to make sure they get some of the action, especially if you have herbivore fish in the display.

One of the great parts about Pithos Crabs is how peaceful they are. They are not going to pick fights with other invertebrates or fish, even other Pithos crabs. You can keep as many females and males as you have food and space for. One crab would be plenty in a 20-gallon aquarium. Females will frequently mate with males in the home aquarium, which will result in them laying eggs, which will usually be quickly consumed by any fish and corals in the tank. They are very low risk with corals; except they might harvest the occasional polyp to decorate themselves with. We hesitate to say any crab is 100% reef safe, but Pithos are as good an option as Emeralds or Hermits in this regard when it comes to peace of mind in your reef displays. Obviously, you shouldn't keep them with inverts that are aggressive, or fish that would love a crabby snack like Puffers or some large Triggers etc.

The Pithos crabs don't get as big as the species of decorator crabs that we frequently see in marine aquariums but will get a bit bigger than Emerald Crabs. You usually see them in your Local Fish Stores at about an inch to an inch and a half across their shells, with a maximum size of about two inches across.

Like all invertebrates, they are sensitive to copper, so don't treat your aquarium with anything that contains copper in any form. Other than that, and making sure they don't get eaten, there's not really anything in the way of specialized care that they need. Are you starting to see why we want to call them Miracle Crabs? No matter what you call them, these crabs deserve a spot in your cleanup crew. Ask your local fish store about getting you some from Quality Marine today!