Maintaining mantis shrimps (Updated April 5,1998)
It doesn't take a rocket scientist to maintain mantis shrimps. I'll bet even a close friend of mine, who has earned the nickname "Sure Death" after some extremely hardy desert plants that I gave her actually died of neglect, would have little problems caring for one. Some people, and I will be kind and not mention any names, have even dubbed these penultimate pests of the reef aquarium the "Roaches of the Seas", a testimony to their hardiness and their ability to resist all human attempts at removal.
Now that you've taken the plunge and decided to maintain a mantis shrimp or two, and in the process gone against the wishes of your LFS, your family, friends, and worried neighbors, maybe you're wondering whether you'll ever be able to show your face again in public. Fear not, oh ye of little faith! Once your loved ones realize how little time and money you'll actually be spending on these critters, as opposed to the tons of dinero and obsessive-compulsive care you've lavished on that mishmash of corals and fishes you had grandly proclaimed "My Grand Reef", they will all fall instantly in love with your new (but cheaper!) obsession.
Take the maintenance of water conditions, for example. In most marine aquaria, the owners worry endlessly about pH, salinity, nitrification, denitrification, and the hardness of the water, not to mention the presence of nitrates, nitrites, chlorine, phosphates, copper, ammonia, and ammonium (and uranium and platinum, for all I know). The source of the water is also a problem, with fancy terms like reverse osmosis and ion exchangers being tossed around like there's no tomorrow, all of which are guaranteed to scare the living heck out of beginners and potential converts to the field (who probably wished after awhile that they had stuck to FW instead).
Me? I take some tap water, let it stand for 24 hours and/or treat it using a tap water conditioner (to remove excess ammonia, heavy metals, etc), make sure the salinity is within bounds (around 1.022 specific gravity) and the temperature is between 24 and 28 degrees Celsius, then plop the mantis shrimp into the tank and watch it duck into the nearest burrow or cavity. I check the salinity of the water and make up for evaporation daily (the small tanks used for mantis shrimps makes this necessary), and do partial (25%-35% or so) water changes every two weeks (for 10 gallon tanks) to keep the water relatively clean. Other than that, I pretty much don't bother with chemical checks (although I do check ammonia levels for the smallest tanks every time I feel the water has become "smelly" or cloudy for some reason or the other). Since chemical reagent kits usually costs in the tens of US dollars for only 10-20 tests, I figure opting for mantis shrimps as opposed to relatively more delicate marine invertebrates and fishes will have saved me enough money over the course of a year to buy a new Hyundai.
Filtration is also not a problem when you maintain stomatopods. Although I discourage this, I have heard of people who simply stick mantises they have caught in their reef tanks into containers without filters, and the critters do fine given enough food and partial water changes every once in a while. I myself use either traditional undergravel or power filters (which provide biological, physical, and some chemical filtration), and I'm sure the mantis loves me for this. You may also elect to skip the filter and do water changes biweekly after every feeding, since the mantis shrimps seem to be relatively picky eaters when they find out you've become their literal slave and are a regular source of food.
Mantis shrimps will generally switch to "dead" food relatively easily, once they've figured out it's either that or face a radical crash diet (I absolutely refuse to feed them live food every day). I feed them bits of shrimp (thawed from the freezer and bought at the local Pathmark store), as well as bits of mussel, squid tentacles, and crushed snail bits. I noticed that the enthusiasm for frozen foods varies between species, and maybe even among individuals. Most individuals will gladly take their daily rations from my "chopsticks" and munch enthusiastically with their upper bodies and heads sticking out of their cavities, while a few will throw out the things repeatedly. In this case, if you keep bothering them with it (i.e. keep sticking the food into their burrows/cavities) they usually relent and finally take a few bites out of the food. You may also elect to feed them less frequently (twice a week or so), in which case there will probably be less leftovers. I have not had the chance to feed them live food, although others have fed their large Odontodactylus specimens one goldfish and the like every day. I once introduced FW crayfish into the tank of a well-fed Gonodactylus individual, but all the mantis did was easily bounce the large crayfishes off the walls everytime the things wanted to go into the mantis shrimp cavity (one unlucky crayfish run well into the cavity of the mantis shrimp, prodded by the cruel author of this piece, and was promptly stunned then killed by the mantis, which then threw the body out of the cavity).
One thing that you must absolutely provide for the mantis shrimp, which is generally a cavity dwelling smasher, is some type of artificial burrow or cavity. Although some people may hesitate to do this, fearing that their "investment" might simply lay in there and not show off its luscious bod, mantis shrimps are retiring creatures that need to feel secure within the confines of an enclosed space. If you do not provide them with any shelter, they will most likely "crouch" by one wall of the container, their flanks pressed tightly against the cold and unyielding surface (hmmm, sounds like I've read too many romance novels*), and slowly and surely waste away. I generally provide my specimens with a long plastic tube (with an entry diameter 1.5-3x the diameter of the mantis shrimps), which I completely bury under pebbles or sand (in order to keep the inside of the tube dark), with only one or two entryways uncovered. The smaller mantis shrimps also seem to be satisfied making their homes inside abandoned snail and hermit crab shells, which in addition provide extremely attractive decorations inside the tank.
Lighting? Vas is das lighting? Instead of using expensive,metal halide or high-intensity fluorescent bulbs, I generally stick to regular fluorescent or even incandescent bulbs. In the case of the latter, it would be wise to make sure the temperature in small containers does not get unduly heated by the lighting. In every case, I use a 12 hour light, 12 hour dark cycle, usually through the use of preset timers. All the mantis shrimps, at one time or the other, will regularly close off the entranceways to their cavities at night, using pebbles or any other handy, and manageable object lying around. They will also do this for one or two days straight if molting.
One warning about maintaining mantis shrimps, though. According to Dr. Caldwell, although they are extremely hardy species in many ways, they are relatively susceptible to succumbing to volatile organic solvents. Waxing the floor close to these critters, for example, will probably kill them.
Some final advice to the faint-hearted. Firstly, it goes without saying that you must keep only one mantis shrimp per tank, unless you have a really big tank and numerous cavities provided for these territorial animals, or are in the process of studying stomatopod agonistic interactions or mating habits. The one time I temporarily placed two individuals in the same tank, the two ended up fighting (and scaring the heck out of me). Secondly, I occasionally find myself greeting one of the mantis shrimps, or talking to it soothingly during feeding. If you catch yourself doing this, stop, and remind yourself that, although they may be relatively alert critters with a penchant for looking intelligent, mantis shrimps generally do not understand Tagalog or English (nor any other human language as far as I know). In addition, I have not seen any reports of these animals growing more healthy if given enough pep talk by their handlers. Finally, enjoy your new keeps. Study them, learn more about their habits and behavior. Contribute to our knowledge of these fascinating animals.
Alan San Juan (Airlan).
* just kidding. really. i tend to read sf and horror.
Web Site Author: A. San Juan
Site Created February 3, 1998