When it comes time to choose your reef tank invertebrates, you’re spoiled for choice. And you’ll find plenty of popular options. But have you considered the pistol shrimp? This amazing crustacean often slides under the radar with hobbyists (a tongue-in-cheek joke if you aren’t familiar with the species). It isn’t as famous as the cleaner shrimp – especially the fire shrimp and skunk cleaner (for an excellent reason) – but that doesn’t mean the group isn’t every bit as fascinating. And if you haven’t considered adding one to your tank before, you will now!
Table of Contents: Pistol Shrimp
When it comes to pistol shrimp, there are TONS of information to sort through. And you can use the links below to hop down to a section that interests you. But if you want to learn all of the ins and outs for the group (which you will once you start on the dive), keep scrolling to read the full article. They’re not the most challenging saltwater shrimp species you’ll come across. However, they have some famous quirks that can make tank life…let’s say “interesting.”
- Introduction to Pistol Shrimp
- Quick Facts
- How the “Pistol” Works
- Aquarium Care for Pistol Shrimp
- Pistol Shrimp Compatibility
- Symbiosis with Shrimp Gobies
- Are Pistol Shrimp Right for Your Tank?
- For More Information
With a name like “pistol shrimp,” you know there’s a story brewing. And you’re right. This crustacean comes with two fascinating behaviors, the first of which centers around that common name. (Don’t worry, we’ll tackle the second a bit later) Pistol shrimp possess loaded weapons in their claw. No, seriously!
The claw of the species in the Alpheidae family is modified to create a “bullet” of water. The projectile’s strong enough to stun and even kill small fish (depending on the size of the shrimp). And as the bubble collapses? It creates a pulse of energy that generates light AND sound. You can hear the “pop” coming from your aquarium. And if you’re out in the ocean? It’s audible there, too! Scientists have recorded the sound throughout the world’s oceans!
Of course, if you’re expecting a dramatic “bullet” ricochet, you’re in for a disappointment. It’s more of a “snap.” And that’s why you might see them listed in your local fish store as snapping shrimp. (The size of the crustacean plays a big part in the sound they generate with those claws) If you’re curious about what these water bullets sound like, take a listen to this YouTube video, recorded in an aquarium (Note: that “smoke” is nothing more than the energy released from the bubble collapsing):
The other behavior pistol shrimp are famous for? Their symbiotic relationship with shrimp gobies. If you take a look at the invertebrates, you’ll notice their short eyestalks. Some even get lost under the carapace. This translates to poor eyesight. So pistol shrimp started pairing up with shrimp gobies to gain better vision. Both species burrow, and they share the same tunnel. The goby stays out front, scanning the surround for potential problems. Meanwhile, the shrimp keeps one antenna on the goby’s tail. When they feel the warning signal, they know it’s time to bolt.
The pair benefits from the relationship by sharing a home and often food resources. Not to mention pistol shrimp have the better digging skills – repaying gobies for their keen eyesight. It’s a mutualistic partnership – and one many hobbyists like to display.
- Common Names: Pistol shrimp, Snapping shrimp, Alpheid shrimp
- Scientific Names: Alpheus spp.
- Reef-Safe? Likely safe with corals – not with small prey (small fish, mobile invertebrates)
- Diet: Carnivore
- Care Level: Easy/suitable for beginners
- Unique Aspects: Symbiosis with shrimp gobies, uses “pistol” to stun prey
- Warnings: Watch for high nitrates; NEVER use copper in the tank
Admit it, it’s the water bullet that caught your attention. And there’s a good reason for that: It’s cool! How often can you discuss the fact one of your invertebrates can shoot water bullets? Even the scientific community finds them fascinating.
But how does that pistol actually work?
Pistol shrimp tend to have one claw that’s larger than the other. That larger claw works as the “gun.” The shape, when snapped closed, creates a cavitation bubble (the easiest way to think of it is the pocket on bubble wrap). It’s a short-range “bullet” of water and compressed energy. If you look close enough, you’ll see the pulse of light the energy produces as the bubble pops.
When the crustacean goes hunting or needs to defend itself, it clicks the claw open (like cocking the hammer on a gun). When it’s ready to fire, the claw snaps shut and fires the water bullet. Depending on the size of the pistol shrimp, that bubble moves as fast as 60mph (97kph)! That’s enough to stun the target (either prey or predator) or at least warn it away. It also makes the distinct snapping sound the invertebrate’s known for.
Want to see this weapon in action? Check it out in the YouTube video below. (If you have a soft spot for skunk cleaner shrimp, you may want to skip it)
Of course, as cool as water bullets and stunning prey ARE, the actual purpose of the mechanism is for territory disputes. Pistol shrimp use the popping sound to warn rivals away from the burrows more often than they hunt or “frighten” away predators. They don’t see well, and their natural camouflage works against them. So that snapping keeps other shrimp from stumbling into their territory. (Not as cool as firing bullets at big, bad predators, but still pretty awesome)
Now that you’ve decided you need that fantastic “shooting” skill in your saltwater aquarium let’s focus on what you need to keep a pistol shrimp. Luckily, while the mechanism behind their adaptation is complicated, their care ISN’T. Even a beginner to the hobby can manage one without too much trouble. You need a fully cycled tank, of course (as you’d expect for a crustacean), and you need to keep water parameters within healthy levels. But otherwise? They’re not demanding.
Most pistol shrimp prefer to spend their time in dimly lit areas in and around their burrow. They venture out at night to explore and search for meals. A nice sandy or crushed coral substrate will encourage their natural tendency to dig and tidy up that burrow. You DO need to secure all of your live rock and other structures, though. They may dig underneath the rockwork in their excavations, and you don’t want them to get trapped or cause a tumble. (Or, worse, you don’t want them to squish themselves).
What do pistol shrimp eat?
The pistol shrimp is a carnivorous hunter and opportunistic scavenger, eating smaller invertebrates or fish, stunned by its snapping claw, as well as tiny scavenged morsels of meaty foods, algae, and detritus. They are often fed flakes, pellets, and frozen foods in a home aquarium.
If you don’t, you can expect your pistol shrimp to start looking at their tank mates with a hungry eye. They’re reef-safe and won’t go after coral polyps. But small shrimp and other invertebrates? Yeah, they’re on this carnivores menu. It’s better to err on the side of caution and make sure you keep your shrimp happy and well-fed. (Don’t worry, you’ll still get to hear those water bullets pop. If the pistol shrimp feels threatened in any way, they’ll use one to warn-off the predator)
Despite their carnivorous nature, you don’t need to keep pistol shrimp on their own. Even the largest species don’t get more than 3 inches (7.6cm) long. This means you can safely pair them up with most of your favorite fish species. Of course, you want to avoid fish that think shrimp taste delicious, such as hawkfish and lionfish. Oh, sure, you’ll hear plenty of popping as they attempt to warn those predators off with water bullets. But is it fair to put them in a “shoot out” situation? (Not so much)
And unless you want to restock your tank, you need to consider the safety of your other invertebrates. Pistol shrimp ARE active hunters. They’ll take a look at some of their tank mates and see a delicious midnight snack. You don’t want to put a species in that position. That means avoiding:
But they won’t bother your corals. Some species even establish their symbiotic relationships with sponges, tunicates, and sea urchins. And if you happen to come across the red snapping shrimp (Alpheus armatus)? It likes to associate with the curlicue sea anemone (Bartholomea annulata). They enjoy living in reef tanks, and they won’t cause problems with your more delicate tank selections.
Of course, when it comes to compatibility, that symbiotic relationship with shrimp gobies tops the list. And plenty of hobbyists rank the pairing as a close second behind the water bullet as a reason to add pistol shrimp to their saltwater aquariums. You’ll find several goby species work well with this crustacean, including Yellow watchman and Yasha gobies.
Mutualism results when both species in the partnership benefit equally. And that’s how this symbiosis plays out. The pistol shrimp burrows into the sand or substrate with their legs and claws to create a tunnel. It’s large enough to support the crustacean and their goby partner. But pushing sand (or coral rubble) in and out leaves the shrimp vulnerable to predation.
The goby stands watch while the pistol shrimp works.
With such lousy eyesight, pistol shrimp rely on movement to communicate with their goby roommate.
The Pistol shrimp and the goby communicate with each other through physical contact with the shrimp’s antennae and tail undulations in the water, indicating it is safe to emerge from the burrow (Karpulus 1972).
Placing an antenna on the goby’s tail, they can go about their housekeeping duties while the fish plays lookout. At the first sign of trouble, the goby flicks its tail. The vibration transmits down the antenna, and the pistol shrimp knows to bolt into the burrow. Then the goby can follow. No muss, no fuss – and not a sound needed in the process.
Some gobies also “pay dues” by collecting food to bring back to the burrow. Then the two share the meal. Both species occupy the den – having a safe place to live. The goby doesn’t need to worry about expending energy to dig or maintain the tunnel. And the pistol shrimp doesn’t have to strain those tiny eyestalks trying to watch for possible predators sneaking up on them.
Cleaning behavior has also been observed between the pistol shrimp and its goby companion (Karpulus 1972).
And if you have a pair in your tank, you get to witness the relationship first-hand!
However, there’s a catch to adding pistol shrimp and gobies to your aquarium: There’s no guarantee the fish and crustacean will pair up if you buy them separately. Many frustrated hobbyists have posted about two individuals that spent time together but never “found” each other. And some may even attack or kill the goby! You can’t force the relationship. And assuming symbiosis will happen? Yeah, no such luck.
The best way to ensure a bonded pair is to buy one. You’ll pay a little more, but it’s worth it. And it isn’t tricky to find, either. Plenty of fish stores – such as Blue Zoo Aquatics – offer bonded shrimp and gobies. It’s better than rolling the dice that you’re “matchmaking” efforts will pay off.
Pistol shrimp are certainly not appropriate for every tank. While they’re easy to feed and technically considered reef-safe, they will harass and kill most other small, mobile invertebrates in your tank. So if you want to have hermit crabs or other shrimp, you might want to take a pass on owning these fascinating crustaceans.
If, on the other hand, you’re mesmerized by burrowing species or the symbiotic relationship with a goby – and don’t mind the fact that you won’t be able to keep other shrimps or crabs – the pistol shrimp could be a great addition.
You need to think through the different sides of this unique species. And, yes, that means getting past those water bullets. (Though they are super cool)
Pistol shrimp definitely rank at the top of interesting saltwater shrimp species. They intrigue anyone that comes across them. (Well, once they hear about that shooting skill, anyway. Since, you know, the species don’t tend to stand out all that much) And if you’re looking for even more reasons to consider adding one (or two) to your reef tank, we’ve got you covered there, too.
How about starting with this YouTube video on that symbiotic relationship with gobies?
No one will deny pistol shrimp have incredible features. So why not check out some other unique invertebrates:
Or how about going the other direction and looking into FISH with fascinating adaptations?
What Do You Think?
Have you ever kept pistol shrimp? What has your experience been? Share your notes below!
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Karpulus, I., Szlep, R. & Tsurnamal, M. Associative behavior of the fish Cryptocentrus cryptocentrus (Gobiidae) and the pistol shrimp Alpheus djiboutensis (Alpheidae) in artificial burrows. Marine Biology 15, 95–104 (1972). https://doi.org/10.1007/BF0035363
Koukouvinis, P., Bruecker, C. & Gavaises, M. Unveiling the physical mechanism behind pistol shrimp cavitation. Sci Rep 7, 13994 (2017). https://doi.org/10.1038/s41598-017-14312-