Special relationships: Keeping pistol shrimps and gobies

For those of a scientific persuasion, it’s generally frowned on to assign human behaviour to animals. However, when watching the shrimp gobies and their little crustacean partners, it’s difficult not to!

If you have kept them in an aquarium or seen them in the wild, you will understand what I mean. The slightly neurotic, ultra-clingy shrimp keep in constant tactile contact with the goby. The gobies often appear somewhat fed up with this constant attention. 

It suggests a somewhat dysfunctional relationship, however, it’s a highly effective. More than 100 species of goby show this symbiosis. Luckily, it’s possible to replicate such a fascinating symbiotic relationship in your marine aquarium.

What do the shrimp and goby offer each other?

Several pistol or 'snapping' shrimps of the genus Alpheus associate with gobies. Primarily you can find them in the Indo-Pacific amongst areas of sand and rubble. These shrimp generally inhabit relatively shallow waters of the coral reef.

The shrimp has notoriously poor eyesight, but is good at constructing and maintaining a burrow. In fact, Alpheus shrimp seem obsessed with it. They constantly shift rubble and debris to keep the entrance clear.

The goby, meanwhile, has particularly good vision. But they are less adept at creating burrows which, of course, offer valuable protection on the reef.

In an evolutionary masterstroke, both shrimp and goby have evolved an alliance which utilises the strengths of each. Or perhaps makes each one’s weaknesses less of a hindrance, depending how you look at it.

In return for 'lodgings', the goby acts as a sentinel to the shrimp. The pair use tactile communication virtually constantly.

The goby primarily uses subtle movements of its tail to warn the shrimp if danger is imminent. The shrimp maintains contact with the goby, courtesy of its long sensitive antennae, ensuring it doesn't miss a signal.

Often pairs of gobies or pistol shrimps will inhabit the same burrow. The animals tend to be diurnal and the shrimp will often seal the entrance to the burrow at night to shut out predators.

This is a truly mutualistic example of symbiosis – meaning both partners benefit from the deal. In fact it appears to be, for many goby species, an obligate relationship on the reef. Meaning they have to exist in partnership with their respective shrimp(s) due to their vulnerability to predation. Many species of shrimp goby are always with their crustacean 'landlord'.

A study undertaken by Californian researchers revealed that the shrimp-goby partnership has twice evolved independently. Each event involving different major groups of goby.

Gobies from the genera Amblyeleotris, Ctenogobiops, Cryptocentrus, Stonogobiops, Vanderhorstia, Tomiyamichthys and Mahidolia are all known to show symbioses with shrimp.

Shrimp gobies are frequently available with a wide variety of species offered. The shrimps, one the other hand, are less frequently offered because they are difficult to capture. Primarily, the gobies on offer will include species from Stonogobiops, Ctenogobiops, Cryptocentrus and Amblyeleotris.

Despite the association between the shrimp and their feisty fishy lodgers, you can keep the gobies on their own in the aquarium. Just make sure you include plenty of suitable nooks and crannies to hide in.

However, being the sophisticated aquarist that you are, you want to set up your own shrimp-goby station. Below I outline how you can do just that.

Setting up for that special shrimp goby relationship

You’ll first need to correctly identify the species of both shrimp and goby to get a successful partnership. You may find pairs of gobies and shrimps in your local fish shop's tanks, and these can be a decent bet. But otherwise, research carefully before buying your choice of species.

Both shrimp and gobies require an appropriately furnished fish tank. Plenty of suitable substrate is vital for burrowing and overall a reef system is perfect. But , equally, you could set up a dedicated system specifically to house a shrimp goby pair.

If housing both a shrimp and goby as part of an established system, ensure that tank mates are peaceful. Aggressive or even some semi-aggressive species will harass the goby. They may even out-compete it in the hunt for food.

Otherwise, feeding for both shrimp and goby is straightforward.

The goby will accept a wide range of live, fresh and prepared feeds. They will readily accept frozen mysis, Artemia and prepared foods. Feed them at least twice a day with a variety of options. The shrimp tend to be scavengers, so will happily pick at any leftovers.

The gobies, despite their diminutive size, tend to be territorial with conspecifics. In fact this extends out to other members of the same genus. Limit stocking to just one goby and shrimp pair per aquarium, unless you have several hundred litres available.

You can sometimes establish heterosexual pairs of gobies. If you are lucky enough, you may even find a mated pair hiding in one of the sales tanks. Otherwise, stick to one goby per genus.

A shrimp and goby symbiotic pairing can be ideal for nano tanks. A 100l/22 gal reef tank is adequate for the smaller species. Some burrows may be up to half a metre long, so provide them with plenty of substrate.

The shrimp will need to have a substrate of some 10cm/4” in which to maintain its burrow. Providing only fine sand simply won’t cut it as this structure will readily collapse. The shrimp are good at building burrows, but not that good!

Using some fine sand is OK, but mix this with various other coarser materials. This will allow a stable burrow to be built. Pieces of shell and coarse coral chips mixed in with the substrate are ideal.

Why not take out your frustrations on some small pieces of live rock with a hammer? As well as having therapeutic benefits, this can create instant rubble pieces which your shrimp will love.

Both the goby and shrimp need careful acclimatisation. Being quite shy for several days.

Keep water quality as good as possible, as it’s best to avoid having to carry out any disease treatments. The little gobies can be sensitive to many medications, so ‘prevention is better than cure’ is a sensible approach.

Related article: Gobies for the reef aquarium

Poppers are muted with gobies

Pistol shrimps derive their name from their ability to produce loud popping noises from their specialised claws. Specifically, they create a high-speed cavitation bubble which creates a sound as it collapses. Some species can stun or even kill fish using this technique.

Scientists are using these sounds to quickly assess reef health to target conservation methods. 

However, while they can create sound, those which associate with gobies tend to be small and relatively peaceful. They are highly unlikely to keep you up all night!

Meet the species

The gobies…

Stonogobiops species of goby are small and delicate, rarely reaching more than 7cm/2.8” and have a slender body. This genus includes the fantastically named and expensive S. dracula (dracula goby) from the Indian Ocean. This species is attractive, with alternate thick and thin bands of red-orange.

S. xanthorhinica, at up to 6cm/2.4”, is one of the most regularly seen. They come from a wide area of the Indo-Pacific. ‘Xanthorhinica’ means yellow nosed in reference to its bright facial marking.

One of the most desirable members of this genus is S. yasha from the Western Pacific. Sporting beautiful red markings and growing to no more than 5cm/2”, this might be the perfect marine species. You can clearly see why people use the common name orange striped goby. They’re pricey but worth it.

Ctenogobiops species include the high-fin spangle goby (C. tangaroai) whose rather showbizzy name is derived from its iridescent, spotted markings. It reaches a diminutive 6cm/2.4” and hails from the Pacific Ocean.

Cryptocentrus species include the yellow watchman goby (C. cinctus). A stout, chunky specimen from the Western Pacific, reaching some 10cm/4” in length and having a somewhat grouchy appearance.

C. pavoninoides occurs around Indonesia and goes by the name of blue spot goby. This marine fish can attain 15cm/6” in the wild but is usually smaller in the aquarium. Exclusively from the Red Sea, the Harlequin goby (C. caeruleopunctatus) will reach similar lengths.

Amblyeleotris species are generally slender and colourful. Randall’s goby (A. randalli) from the Western Pacific is one pretty fish, reaching no more than 12cm/4.7”, sporting a prominent dorsal fin and displaying bright orange stripes.

Also from the Western Pacific, the sunspot goby (A. guttata) reaches a similar size and displays distinctive orange spots across its body.

The aurora goby (A. aurora) from the Indian Ocean is a stunning specimen. They can reach 10cm/4” in length and display bright red stripes and a gorgeously-marked caudal fin.

Also worth a mention is Wheeler’s goby (A. wheeleri) from the Indo-Pacific. This fish is reminiscent of an old-fashioned barber’s pole with its alternate red and white stripes, often dotted with fine blue spots. They attain a similar maximum size to the aurora goby.

The shrimps…

Many symbiotic shrimp are often simply labelled 'Alpheus spp.' when appearing in retailers’ systems. Remember to research if the Alpheus species you’re interested in is actually a symbiont with gobies. Many species won’t like the idea of co-habiting with a fish!

One of the best species and one of the most commonly seen is Randall’s shrimp (A. randalli), pictured above with Stonogobiops nematodes. This shrimp is transparent with vivid red stripes interspersed with white banding and yellow-green legs.

This will readily associate with many species of goby, including many Stonogobiops, Cryptocentrus and Amblyeleotris species.

While not the prettiest of shrimps, with brown markings, the tiger pistol shrimp (A. bellulus) is sometimes offered and makes a good choice for pairing with several gobies. For example, it will act as a symbiont with C. cinctus, A. guttata, A. randalli and S. yasha, plus many more.

Alpheus ochrostriatus, the fine-striped shrimp, is another good bet. They are particularly attractive to look at with delicate pink coloration and thin white stripes across the carapace. It pairs with, among others, C. tangaroai, A. guttata, A. randalli and A. wheeleri.

Some species may live symbiotically with gobies if the mood takes them, but they may be primarily non-symbionts.

Bullseye shrimp (pictured here by Haplochromis, Creative Commons)

Take one look at the bullseye shrimp (Alpheus Soror) and it is easy to see why it commands a high price tag. You will rarely see it in the trade but, when they are you might have to fight to be the lucky one to take them home as they won't be in the shops for long.

The orange body, prominent false eyespot and purple legs and claws make this is a particularly desirable species.

This species seems to occasionally pair with gobies, suggesting it’s a facultative symbiont rather than an obligate one.

No guarantees over pairing choices

Appropriate pairings of shrimp and goby largely appears initiated and maintained through chemical cues.

Some species of goby simply won’t act as a tenant with certain species of shrimp. Some are less choosy than others, but, to avoid disappointment, research in advance whether the pairing you have in mind is a natural one. Knowing the exact species is essential for success.

Remember not all Alpheus act as symbionts. While symbiotic species that never encounter each other in the wild can occasionally pair up.

For further guidance on identifying the various species of both shrimp and goby look no further than Debelius and Baensch’s seminal Marine Atlas (Volume 1).

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