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Stomatopods 101 - Basic Care of Mantis Shrimp
Basic Stomatopod Care
Usually considered the scourge of the community reef aquarium, Mantis Shrimp are becoming more and more popular as pets in species aquariums. With some planning, they can be kept with hardy corals and even other animals.
The first time Mantis Shrimp are encountered by hobbyists, they are usually heard before they are seen or the loss of other tank mates causes alarm. Tell tale signs are loud clicking, shells of mollusks and crustaceans piled near a den, and fish that are eaten showing an even bite pattern (opposed to an animal that has lots of bite holes caused by many scavengers). Mantises may eat the shell of their prey for valuable calcium, but if you do find shells look for breaks made to get to meat deep in snail or hermit shells. “Clicking” may be the sign of a pistol shrimp or mantis shrimp, but pistols usually click in ones and twos while hunting or in defense and mantis shrimp may click anywhere from once to many times while hunting, battling or den building. The sound of snail shells hitting aquarium glass is sometimes questioned as the sign of a mantis, but I’d describe the sound to be very “intentional.” For a small one I might compare it to the sound of a pencil snapping, or a larger variety may be as loud as a rock hitting your car windshield.
Spearer or Smasher?
The large majority of live rock hitchhiker stomatopods are smasher varieties. While spearers can den in “found” live rock holes, they usually dig substrate dens. Smasher types are common in holes in live rock or build dens out of live rock rubble. Spearers can be identified by their sharpened smooth raptorial appendages, and Smashers by the heavy calcified “elbow." Many hobbyists prefer to keep spearers so that they can keep snails, hermits and other hard-bodied animals with them in little danger.
Ideal Aquariums
Most hitchhiker mantis shrimp such as Neogonodactylus Wennerae of Florida and others don’t grow larger than 3.5 inches, so a 5-gallon tank or larger is usually a good balance between swim space and not too large a tank that it’s under stocked. O. Scyllarus or Peacock Mantis Shrimp can reach 8 inches and possibly deliver the strongest strike of all stomatopods, so in their case a 10-gallon or larger acrylic tank is a good choice. I've heard of aquarists keeping mantises in Eclipse 6s and larger, and they do seem to be fine since the acrylic is relatively soft, but is likely too thin for species like O. Scyllarus, G. Chiragra and N. Californiensis. That said cases of Mantises breaking their tanks are pretty rare. Acrylic is your best bet for tough smashers, and definitely do not tap on the glass or wave a little red cape in front of it.
Providing a Den
A PVC den is simple and can make your pet more secure, keep it well shaded, which is important to resist shell disease, and can be configured to help keep strikes off of the tank glass. A slightly larger tube than the stomatopods body is sufficient, but you may want to use one large enough so that it may turn around in its den. For a more natural appearance, black PVC, decorating it with rubble, and substrate lining glued with a thin layer of silicone are all ways to improve its appeal to your pet and you. Since they may try to build their den larger, the open ends of the tube shouldn’t be aimed perpendicular with the tank walls. An “L” shaped den placed in a corner is a good way to leave lots of real estate while protecting the tank.
Heaters
The best heater that you could use for a Mantis Shrimp tank in my opinion is a Titanium heater. I love the one that I've got because of its accuracy and the titanium probe is practically indestructible. According to Dr. Caldwell at UC Berkeley, mantises will sometimes attack when a heater light turns on, breaking the glass and electrocuting them in the process. Attacks also occurred when mantises touched hot heaters with their antennae. If you do go with a glass heater, you'll need to sleeve it in a piece of thin wall plastic tubing, or perforated PVC or acrylic. Tape over the heater light if it's showing.
Substrate
As for substrate, Smasher variety mantises will den in live rock or substrate. Dr. Caldwell posted that O. Scyllarus will do fine in sand or crushed coral. Many spearer type mantises are more commonly sand or mud burrowers. Dr. Caldwell states that he provides crushed coral for most of his animals with a section of PVC and they'll dress their dens with crushed coral. In my tank I'd also like sand for maximum filtration capacity, so I may end up with a layer of coarse sand over the 2 inches of fine sand that I have in there now. Live rock can be aquascaped as desired unless you were intending it being your primary filtration. Keep in mind that Mantises are swimming animals and will hunt in the water column. They aren't always down at the bottom, so I'd keep the rock fairly open for hiding places, and for access to remove broken shells of felled prey from time to time.
Filtration
Stomatopods are fairly messy eaters and may bury uneaten food so good filtration is a must. Clean up animals can be a great help if they’re not large enough to become prey themselves. I use a DSB with live rock and mechanical filtration that is cleaned frequently. The same rules apply here as in other tanks. Start with a plan, test and perform water changes to keep things as clean as possible.
Feeding
I've never heard of a problem feeding a mantis shrimp unless it was overfed, ill or preparing to molt. Our pet currently gets pieces of tiger prawn, which divided came out to be about 20 good-sized meal chunks. I'm going to vary the diet using as much fresh seafood as I can including, shrimp, squid, scallops, clams, mussels, fish, etc. Maybe even a tiny bit of fresh Abalone. I have read of them being lazy after being fed lots of shelled prepared foods that they may hesitate to break open food if they can help it. One thing to note is that smashers will sometimes lose their "clubs" if they're not used over time, so it's a good idea if you can, to occasionally feed them whole clams, mussels, crabs or snails in the shell. Also freeze-dried krill are a great media to absorb liquid vitamin supplements. Something I've read that was really interesting was that in studies, Mantises would selectively choose food for the most food benefit that can be opened by the least number of strikes. It seems they're smart enough to plan their diet and energy usage.
Lighting and Compatibilities
Mantis shrimp can be kept easily in modest lighting, and should always have a dark den available for health of their exoskeleton. Better quality light can be used if you plan to keep light loving invertebrates in the same tank, but there isn’t any guarantee that they will be ignored by a mantis shrimp. I currently keep zoanthids and mushrooms with our O. Scyllarus, but some have been “hammered” and disturbed into regression while the mantis breaks and moves rocks in den building. A prized acropora may not be a good idea either since it may be broken just to make a front door. A common question is if more than one mantis shrimp can be kept in the same tank together. While it’s possible, it’s tricky and dependant on each shrimp having a protected space that the other isn’t able to enter. A smaller mantis shrimp should have a close-fitting den that a larger one can’t reach it, especially after a vulnerable molt. Also a bigger mantis should be large enough that a smaller one won’t attack it during a molt. Two near-sized stomatopods just isn’t a good idea and would likely end in a tragic battle.
So why keep one?
Stomatopods are one of the most intelligent and interesting animals kept in reef aquaria. Many are colorful, bold and quickly identify who feeds them, making them very interactive. Other traits include possibly the most complex visual system on the planet, and their well-known powerful strike, which may be the fastest motion in the animal kingdom, in air or water. I hope this answers some questions on caring for these animals, and it’s great to see more hobbyists finding interest in them!
Much thanks to Dr. Roy Caldwell, UC Berkeley for his continued research of stomatopods and support of hobbyists. Dr. Caldwell is currently on sebatical doing a year of field studies.
Hth!
-Rogue
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