Pistol Shrimp are one of the most fascinating creatures on earth. They have one of the few biological projectile weapons known to science. And despite only being 2 inches or less – they are also one of the loudest creatures in the sea!
These tiny crustaceans punch well above their weight when it comes to both defenses and interest as an aquarium inhabitant. What exactly are Pistol Shrimp and how do we care for them?
What are Pistol Shrimp?
Pistol Shrimp have a single modified claw (one is normal sized like a Fiddler Crab) that works almost like a water gun. The lower section of the claw has a chamber for water to collect in and a groove to direct its flow outward. And the upper claw has a plunger that can be forced into the chamber.
When the Pistol Shrimp wants to use its weapon it snaps the claw together with incredible speed, forcing water out of the chamber. The water bullet travels over 60 miles per hour, plenty fast enough to stun or kill other animals the size of the shrimp.
The claw compresses water so rapidly that a cavitation bubble forms that briefly reaches temperatures of 8,000 K (7,700 °C). That’s actually hotter than the surface of the Sun (5,772 K (5,500 °C)!
Light is also generated from a process called sonoluminescence but it’s too faint to be seen by us. Or by the Pistol Shrimp, which is effectively blind.
Pistol Shrimp use this ability for both attack and defense. This can complicate finding tank mates for them somewhat but we’ll go into that in more detail below.
The most common species in the trade are the Tiger (Alpheus bellulus), Randall’s (Alpheus randalli), Bullseye (Alpheus soror), and Red Caribbean Pistol Shrimp (Alpheus armatus). These four are the most beautiful and in highest demand.
That said, there are over a thousand different species found all over the world. If you get a Pistol Shrimp as a hitchhiker on uncured live rock it’s likely to be a drab, possible unknown species. But the care requirements will be the same as with any other Pistol Shrimp.
- Common Names: Pistol Shrimp (Tiger, Red, Caribbean, etc), Snapping Shrimp, Bullet Shrimp
- Scientific Name: Alpheus sp.
- Origin: Worldwide
- Length: 1-2 inches
- Aquarium Size: 10+ gallons
- Temperament: Peaceful to Semi-Aggressive
- Ease of Care: Very Easy
Caring for Pistol Shrimp
Pistol Shrimp are excellent invertebrates for beginners assuming you’re aware of their few demands.
Aquarium Size
Pistol Shrimp are a smaller aquarium species so they don’t need very much space. A 10 gallon aquarium or larger provides plenty of room for them. What’s more important is substrate depth because these shrimp are burrowing.
At a minimum you’ll want 4 inches of substrate depth if you’re aquascaping a tank with a Pistol Shrimp in mind. A deeper substrate is even better but in aquariums this risks creating anoxic pockets if your substrate prevents water from circulating through it, like compacted aquarium sand can.
That said, the best cure for anoxic conditions are burrowing animals like Pistol Shrimp! You can also add Brittle Starfish, snails, and other burrowing creatures to ensure a deep substrate remains aerated.
Substrate choice also matters for Pistol Shrimp. Sand substrates are not always ideal because sand tends to collapse if the shrimp digs horizontally. If the substrate has enough vertical depth this is less of an issue but doesn’t give the shrimp as much “creativity” in burrow design.
Crushed coral works better because the burrow will hold its form better as the shrimp digs horizontally. Pistol Shrimp are expert architects and you should provide them with a wide variety of pieces to reinforce their burrows with.
Small chunks of rock or coral often disappear into the burrow to build pillars to hold things in place. They may also reinforce the entrance with bits of rubble.
Water Conditions
Pistol Shrimp are one of the least demanding invertebrates you can own when it comes to water conditions. They prefer standard marine conditions: the temperature should sit between 72-78 F and the specific gravity (salinity) should test at 1.023-1.025.
The pH should be from 8.0-8.4, which should be easy to maintain with a crushed coral substrate. Pistol Shrimp are slightly sensitive to nitrite and nitrate buildup, as are all invertebrates. So don’t get too lax on water changes or filter maintenance. But they aren’t nearly as sensitive as corals or anemones.
Pistol Shrimp are highly sensitive to medications that contain copper, however. Copper is lethal even in minute quantities to most invertebrates. If your fish needs treatment for a disease, don’t treat the entire tank with medicine as the shrimp may be killed by it.
They are especially sensitive to medications that target parasitic infections, which are usually caused by invertebrates and therefore use copper-based compounds. Move your sick fish (or just the Pistol Shrimp if all of your fish need treatment) to a quarantine tank.
Are Pistol Shrimp Reef Safe?
Pistol Shrimp are reef-safe. They won’t eat, disturb, or bother corals and sessile invertebrates in any way. These shrimp are entirely carnivorous and so long as you keep them well fed they actually get along well with most aquarium inhabitants.
The only problem Pistol Shrimp might cause to a reef aquarium is through their digging habits. Coral frags that are loose may be plucked up and used by the shrimp to reinforce its burrow. They especially love loose chunks of coral to create a sturdy doorway.
Pistol Shrimp burrows can be very intricate affairs that stretch inches or even several feet in a large aquarium! This can undermine the stability of your aquascape over time and cause corals to shift or even collapse!
But this is very rare and usually happens in tanks where things aren’t properly balanced to begin with. As long as your live rock is securely set, a little digging by your Pistol Shrimp isn’t going to make a difference.
Feeding Pistol Shrimp
Pistol Shrimp are entirely carnivorous but are not picky when it comes to food. Dead meaty foods like cut seafood (fish, shrimp, squid, etc) are the best things to offer. A piece of meat 2-3 times a week is all a Pistol Shrimp needs.
These shrimp are shy and may bolt even if food is placed in front of them. A small piece dropped into the entrance will eventually be consumed, though (or pushed back out if the Pistol Shrimp isn’t hungry).
You can also offer them prepared foods like flakes and pellets. It’s not a good idea to make your shrimp rely on leftovers from other fish because they don’t like wandering out of their burrows for long. They may eventually become tame with frequent feeding and can even be fed by hand.
But if their snapping claws concern you a pair of feeding tongs are a wise investment.
Tank Mates for Pistol Shrimp
Here’s where things can get a little challenging for Pistol Shrimp keepers. Pistol Shrimp, like all crustaceans, are hungry opportunists. If it’s small and fleshy they will try to overpower it and consume it. I would avoid keeping Pistol Shrimp with much smaller species, such as Sexy Shrimp (Thor amboinensis) unless they have an anemone to call home.
Larger Cleaner Shrimp (Lysmata amboinensis), Banded Coral Shrimp (Stenopus hispidus), Arrow Crabs (Stenorhynchus seticornis) will be safe as they are larger than the Pistol Shrimp and have very different habits.
Pistol Shrimp are really territorial more than aggressive. They effectively blind beyond the range of their antennae and hate leaving the safety of their burrow. Anything that isn’t trying to force its way into their burrow is going to be safe. And even then, smaller creatures like snails and hermit crabs are usually pushed out by the shrimp instead of attacked
This means smaller saltwater fish that also like holes in the sand are at risk, such as many Gobies, Firefish, and Blennies. Unless you’re keeping a Watchman Goby alongside your Pistol Shrimp, I’d be careful with these fish. The alternative is to ensure your tank has enough hiding places to satisfy your Gobies so they won’t try to enter the Pistol Shrimp’s lair.
Pistol Shrimp are also fish-safe so long as the fish can’t make a meal of the shrimp. Despite having a literal gun strapped to its arm the shrimp is still a very tiny creature. Larger fish may still make a meal out of it. Lionfish, Groupers, Eels, and other predatory fish are to be avoided.
Specialist invertebrate hunters like Pufferfish, most Wrasses, and Triggerfish can take a faceful of urchin spines without flinching. Your Pistol Shrimp will simply be a spicy shrimp cocktail for them so don’t risk it, even if the fish is small.
Good Tank Mates for Pistol Shrimp:
- Damselfish, Pygmy Angelfish, Tangs, and other small to medium sized fish
- Watchman Gobies
- Corals, Anemones, and Sponges
- Most Shrimp and Crabs
- Snails, Clams, Starfish, and Hermit Crabs
Poor Tank Mates for Pistol Shrimp:
- Lionfish, Puffer Fish, Triggerfish, and other Predators
- Small Fish or Shrimp that might enter its burrow
Pistol Shrimp and the Watchman Goby
Watchman Gobies are by far the best tank mate for a Pistol Shrimp. Both the shrimp and the goby can live alone but when put together they often form a bond with each other. This pairing is called a symbiotic relationship. Both organisms benefit from living side by side.
In this case, the shrimp benefits from the sharp vision of the Watchman Goby. True to its name, this fish sits right at the entrance watching everything that happens around it like a little sentinel. The shrimp is nearly blind but keeps an antennae touching the goby at all times.
If the Watchman Goby bolts into the hole the shrimp knows something dangerous is nearby and follows it. And the goby benefits from the shrimp’s ability to dig deep tunnels. Watchman Gobies can build their own very basic tunnel in loose sand if they are alone. But they can’t dig nearly as well or as deep as a Pistol Shrimp can.
Watchman Gobies are also quite beautiful fish and are very hardy. Some easy to find species include Diamond Watchman Goby (Valenciennea Puellaris), Yellow Watchman Goby (Cryptocentrus cinctus), and Bluespotted Watchman Goby (Cryptocentrus pavoninoides).
The Watchman Goby will eat the same thing as the Pistol Shrimp: Mysis or Brine Shrimp along with prepared foods like flakes or pellets. They also provide an indirect benefit of protecting your other fish.
The Watchman Goby will interact with any fish or invertebrates that try to enter the burrow before the shrimp can detect them. This can save clumsy fish from being injured by the shrimp, which shoots first and asks questions later.
Breeding Pistol Shrimp
Breeding Pistol Shrimp is extremely difficult to do and only happens in aquariums due to happy accidents. The shrimp are simply too territorial. That said, it can be done if you select a male and female who then meet up and like each other.
Your best bet is to buy both shrimp at the same time and introduce them to a new tank simultaneously. That way, they don’t have rigid territorial boundaries to defend. As they begin building they will eventually encounter each other and may even pair up naturally at that point.
The two Pistol Shrimp then form a bond and share a tunnel with each other. They may even tolerate a Watchman Goby as a third roommate. Sexing Pistol Shrimp can be done by size. Males of nearly all species are significantly larger and have a more well developed snapping claw.
Female Pistol Shrimps select for mates based on size. A larger male with a bigger claw is seen as more attractive than a smaller, less well endowed one. That said, you should be cautious with applying these tips with species other than the four mentioned previously.
There are over a thousand different kinds of Pistol shrimp with different habits. Some are even eusocial (Synalpheus regalis). They live like bees, ants, and wasps in huge colonies where a giant queen is the only shrimp that breeds!
But for the more “traditional” Pistol Shrimp, once they pair off, you may see fertilized eggs hanging under the abdomen of the female at some point. The length of time it takes for them to develop depends on the species but for most shrimp it takes 3-4 weeks.
Once the eggs start to hatch the female fans them out into the water column. Shrimp larvae are planktonic at first and take weeks to grow into visible shrimplets. Unfortunately at this stage they get eaten by coral, plankton-eating fish, or simply sucked up into the filter.
But you might get lucky and have a few survive to the shrimplet stage. They will scavenge until they are large enough to dig their own burrow and grow into adult Pistol Shrimp!
