Re:Collecting feeder shrimp for food

Pete Giwojna

Dear Haynes:

Yes, sir, it’s perfectly acceptable to collect live foods for your seahorses. I know many hobbyists and breeders who collect live Mysis opossum shrimp, Caprellid skeleton shrimp, Gammarus amphipods, glass shrimp and grass shrimp for their seahorses with excellent results. For example, Neil Garrick-Maidment feeds his seahorses primarily on live Mysis he collects from the sea and has had seahorses that live for over seven years with the live Mysis as their staple diet.

Here is some additional information on collecting and culturing these live foods from my new book (Complete Guide to the Greater Seahorses in the Aquarium, TFH Publications, unpublished) that you may find useful.

MYSIDS (Opossum Shrimp)

Pros (Giwojna, Oct. 1996):
· Excellent food value.
· A favorite natural food that all large seahorses attack greedily.
· Thrives in saltwater: feed and forget — will survive until eaten.
· Can be easily collected at times.
· Cultured Mysis are available.

· Challenging to culture for the home hobbyist.
· Inland hobbyists have no opportunity to collect them.

Collecting Tips:

Mysis shrimp follow a daily rhythm in their movements, regularly forming dense shoals over sandy bottoms or amidst seaweeds10, and they can sometimes be collected in vast numbers while shoaling by seining or dragging a large aquarium net through mats of vegetation (Giwojna, Oct. 1996). Look for a shallow, sandy, weedy area at low tide during the day, and you can often see them swimming in the weeds or settling on the sand. If there is a significant current, they will congregate in slack water areas on the down-current side of objects. Once you have spotted a likely location, return at dusk when they are more active and net them as described above (Bentley, 2002).

A large net with very fine mesh works best for collecting mysids. I suggest a net with a mouth at least a foot square and mesh less than 1 mm square (Bentley, 2002).

Likewise, mysids are sometimes concentrated in large numbers in tidal pools on mudflats and grassflats by the falling tide. The stranded Mysis can easily be netted from these pools at low tide.

Culture Instructions (Bentley, 2002):

Specific gravity: 1.016 for estuarine species;
pH: 7.8-8.3 (reproduction stops if the pH falls lower than 7.4);
Photoperiod: 14 hours of daylight provided by two Gro-lux fluorescent tubes.
Temperature: 77 degrees F (25 degrees C)

The following guidelines are based on Maureen Bentley’s methods for culturing Mysis (Bentley, 2002). The main culture tank should be large, well aerated, and heavily filtered. I suggest undergravel filtration in conjunction with external biological filters. Mysids are extremely sensitive to water quality, and a good protein skimmer is vital for this reason (Bentley, 2002). Natural seawater is much preferable to artificial, and if you are using a synthetic mix, it’s best to allow the artificial saltwater to age at least one month before use (Bentley, 2002).

When stocking the main tank, introduce the shrimp gradually until you’ve reached a density of about 20-40 adults per gallon (Bentley, 2002). Overcrowding leads to fighting and dead broodstock. If you notice lots of mysids jumping out of the water, the tank is very likely overstocked (Bentley, 2002).

Small quantities of mysids can be harvested daily using a small glass tank equipped with an air-operated undergravel filter. Place 15 to 20 large gravid females in the small tank, returning them to the main tank as soon as they have released their young (Bentley, 2002). (Mysis are cannibalistic and the young must be separated from the adults.) The young can then be raised in the small tank for a short period.

Feed them newly hatched Artemia nauplii or rotifers twice daily until they are a few days old (Bentley, 2002). After a few days, begin supplementing their feedings with marine flake food on occasion, especially brine shrimp flake food (Bentley, 2002).

A feeding frenzy will follow the introduction of live food, which can help you determine the right amount to feed. When fed the proper amount, this frenzy should last around 15 minutes, during which all the live food should be eaten (Bentley, 2002). You will know you have fed enough when the normally transparent mysids have orange stomachs after feeding on the baby brine shrimp (Bentley, 2002). If the adults — especially the males – start eating numbers of the younger Mysis, that’s a sure sign of underfeeding (Bentley, 2002).


Mysidacea, or Opossum Shrimps, are found worldwide. They are small shrimplike crustaceans with a heavy carapace covering their thorax. They are commonly called opossum shrimp because the females carrying their developing young in a bulging pouch or marsupium formed by thoracic plates at the base of their legs (Giwojna, Oct. 1996). The average life span is about 12 months and adult mysids seldom exceed 1 inch in length. At least 460 Mysis species are found around the world (Bentley, 2002), and wherever opossum shrimp occur, they form a large part of the indigenous seahorses’ natural diet. They are snapped up greedily by even the most finicky syngnathids, including the fabulous but delicate Seadragons (Phycodorus and Phyllopteryx sp.). In fact, large seahorses are so fond of these crustaceans that they scarf up frozen Mysids with relish. This is superb food that should form the basis of your seahorses’ diet if you can possibly obtain it–live, fresh, or frozen (Giwojna, Oct. 1996).

Pros (Giwojna, Oct. 1996):
· A highly nutritious, natural food for large seahorses.
· Available from pet shops or aquarium stores as well as through the mail.
· Very easy to gut-load and enrich with various supplements
· Good tolerance for saltwater: brackish ghosts last surprisingly long, and even freshwater ghost shrimp survive long enough to be a very useful food.
Cons (Giwojna, Oct. 1996):
· Suitable only for the largest specimens.
· Often too expensive to use more than occasionally.
Collecting Tips:
Ghost Shrimp are seasonally abundant along the Gulf Coast of the US in salt marshes, rivers that empty into the sea, tidal creeks and brackish bays (Ricketts, Robert T. 2003). Brackish Ghosts can be collected easily at low tide by vigorously shaking clumps of floating seaweed into a bucket of seawater, or by dragging a small seine or large aquarium net through tidal creeks or the grass flats just offshore (Giwojna, Oct. 1996). Similar techniques will often produce freshwater Ghost Shrimp from fresh streams or waterways, including grassy canals and ditches (Giwojna, Oct. 1996). Harvest only specimens that are small enough for your seahorses to swallow whole.
Aquarium specimens are available year round. Fish stores carry Ghost Shrimp both as feeders and as oddball pets for freshwater hobbyists (Giwojna, Oct. 1996).
Culture Instructions:
Ghosts do not thrive in soft water, so for best results keep them in slightly hard to alkaline water (Ricketts, Robert T. 2003). Like all crustaceans, these see-through shrimp shed their exoskeletons in order to grow. They may have difficulty molting and become stuck halfway through the process of extricating themselves from their old exoskeletons, particularly in soft water that is deficient in calcium (Ricketts, Robert T. 2003). For this reason, I recommend gradually converting your holding tank for Ghost shrimp to brackish conditions, using a high-quality marine salt mix to slowly raise the salinity (Ricketts, Robert T. 2003).
There are at least two distinct types of Ghost Shrimp (very likely more), which are very difficult to distinguish by casual examination (Ricketts, Robert T. 2003). One category of Ghost appears to be a true freshwater species. The freshwater Ghosts do not tolerate full-strength saltwater for any length of time but withstand brackish conditions without difficulty (Ricketts, Robert T. 2003). The other category of Ghost Shrimp is a brackish species that can be converted to full-strength saltwater, but which also tolerates freshwater for extended periods (Ricketts, Robert T. 2003).
One possible way to determine which type of Ghost Shrimp you have is to examine females that are "in berry" (carrying eggs attached to their swimmerets). The saltwater or brackish Ghosts carry huge numbers of extremely tiny eggs (Ricketts, Robert T. 2003). So small are these that individual eggs cannot be seen with the naked eye. The eggs of freshwater Ghosts are said to be much bigger so that separate eggs are visible (Ricketts, Robert T. 2003).
The freshwater Ghosts breed more readily in the aquarium, and the larval shrimp are somewhat easier to raise (Ricketts, Robert T. 2003), but home culture of Ghost Shrimp is not really practical regardless of which variety you obtain.
Feed Ghosts small amounts of dry food once daily. The fine, leftover particles that accumulate on the bottoms of nearly empty flake food containers are great for feeding Ghosts, or crumble fresh flakes between your fingers to create particles of that same consistency (Ricketts, Robert T. 2003). Soak these fine flakes in a good enrichment formula and then feed them to the shrimp about 30 minutes before feeding the Ghosts to your seahorses (Ricketts, Robert T. 2003). This will gut-load the shrimp and fortify them for maximum nutritional value. (You will actually be able to see the enriched flakes accumulate in the hindgut through the shrimp’s transparent body.)
A 10-15 tank will hold quantities of ghost shrimp, and smaller numbers will do fine in a 5-gallon bucket equipped with an airstone or air-driven foam filter (Ricketts, Robert T. 2003). Sponge filters will suffice; change water once a week to maintain water quality (Ricketts, Robert T. 2003).
These shrimp are all but transparent, which explains why they are universally called ghost shrimp or glass shrimp. Their exoskeletons are perfectly clear, the underlying muscles nearly transparent, thus clearly revealing their internal organs and GI tract (Ricketts, Robert T. 2003). A loss of transparency is a sign of severe stress and poor health; upon death, Ghosts typically turn an opaque white like their namesakes (Ricketts, Robert T. 2003). Ghost shrimp are acrobatic swimmers, which propel themselves backward with amazing speed by flexing their tails beneath them.
Fully-grown Ghosts can reach two inches in length, but the best feeder shrimp for the greater seahorses are 1/10 to 1/4 that size, so select your specimens accordingly (Ricketts, Robert T. 2003). Hobbyists estimate that 100 eating-size Ghost shrimp is roughly a one-week supply for two large seahorses. With the high unit cost per shrimp, it’s easy to see than keeping your herd on a staple diet of store-bought ghosts is a very expensive proposition!

Pros (Giwojna, Oct. 1996):
· Highly nutritious, hard-bodied crustaceans.
· Favorite food of many larger seahorse species.
· Good tolerance for saltwater (marine Gammarus survive indefinitely and even freshwater Gammarus will last until eaten if your sea horses are fond of them).
· Live Gammarus are increasingly available as fish food.
· Starter cultures are widely available through the mail.
Cons (Giwojna, Oct. 1996):
· Slow reproductive rate makes it difficult to raise them in large quantities.
· Slight risk of introducing disease with Gammarus collected in the wild.
Collecting Tips:
Marine Gammarids–Gammarus locusta, a marine amphipod, can often be found in large numbers at the seashore by overturning rocks and coral rubble at low tide (Giwojna, Oct. 1996). Also know as scuds or beach-hoppers, scads of the land-dwelling form of these amphipods (Talitrus saltator) can often easily be collected from the mats of seaweed washed up on shore at the tide line. Simply gather up clumps of the freshly deposited seaweed and shake it vigorously over your collecting bucket to dislodge the amphipods.
Freshwater Gammarids–Gammarus fasciatus can be collected from vegetation and leaf litter on the bottoms of ponds and slow-moving streams (Giwojna, Oct. 1996).
Culture Instructions:
Marine Gammarus will maintain a self-sustaining colony if established in a standard saltwater aquarium with coral gravel and rubble and left undisturbed while their population grows (Giwojna, Oct. 1996). Encourage a lush growth of green algae and restock periodically.
Under the right conditions, these small, shrimplike crustaceans mate and reproduce readily in captivity. Provide them with a lush green mat of Ulva macroalgae as natural habitat, and they will soon take up residence and establish a breeding colony of amphipods (Indo-Pacific Sea Farms, 2003). Provide them with low light levels, good aeration, and a pinch of flake food twice a week and you’ll soon have a growing population of Gammarus to dole out to your seahorses (Indo-Pacific Sea Farms, 2003).
Freshwater Gammarus can be cultured in a plastic wading pool or similar spacious receptacle equipped with an airstone (Giwojna, Oct. 1996). Feed sparingly with chopped raw spinach, Spirulina, or a pinch of dry fish food. Include plenty of algae-covered rocks and driftwood for shelter, and position where strong direct sunlight will produce heavy algal growth (Giwojna, Oct. 1996).
To feed these 1/4"-5/16" crustaceans to your fish, siphon water from around the rocks, shells, and gravel in the culture tank and strain it through a net to separate the Gammarus from the debris (Giwojna, Oct. 1996). Commonly known as side-swimmers, these hard-shelled amphipods have a herky-jerky, sidestroke swimming style that most large sea horses find irresistible (Giwojna, Oct. 1996). Their seemingly frantic movements and tendency to dart out from hiding suddenly seldom fail to trigger a sea horse’s feeding response, and this is one food hungry Hippocampines will actively pursue and search out. Some sea horses will even accept freshly killed or dead Gammarus (Giwojna, Oct. 1996). An ideal food: substantial enough to be your sea horses’ staple diet, if you can obtain it in sufficient quantity!
When mating, the male amphipod carries the smaller female grasped between its legs, a breeding method known as amplexus (Biology of Amphipods, 1996). Thus, when you see pairs swimming together while locked in amplexus, it’s a sure sign your amphipod colony is growing. The female subsequently releases the fertilized eggs into a ventral brood chamber where the unattached eggs are held by extra branches of her walking legs and incubated during development (Biology of Amphipods, 1996).
Unlike crab and shrimp larvae, baby amphipods are not released as zoea that develop into adults after several stages of metamorphosis (Biology of Amphipods, 1996). Instead, the young look like miniature versions of their parents when released, and some species even show parental care of their young after they leave the brood chamber (Biology of Amphipods, 1996).
Different types of amphipods move differently, depending on the arrangement of their legs. Most species can walk upright, scuttling along by using most of their thoracic legs, but this is a slow, rather cumbersome method of locomotion (Biology of Amphipods, 1996). Practicing their sidestroke and swimming along using three pairs of pleopods is much faster (Biology of Amphipods, 1996). But the true specialty of amphipods is the tail-flip, a rapid escape response where the abdomen flicks the animal away after the uropods are dug into the substrate (Biology of Amphipods, 1996). Terrestrial amphipods (scuds, sand fleas, beach hoppers, etc.) are especially adept at this startling maneuver. It is this variety of frantic movements and escape maneuvers that triggers the seahorse’s feeding response and makes amphipods so irresistible to Hippocampus. Seahorses love to hunt them!
As we’ll see below, Caprellids cannot use any of the amphipod’s usual methods of locomotion. They are restricted to slow-motion somersaults and painstakingly stepping along like an inchworm.

CAPRELLID AMPHIPODS (Caprella acutifrons)
· Relished by all the greater seahorses.
· Excellent nutritional value.
· Feed-and-forget: survive indefinitely in saltwater until eaten.
· Difficult to obtain.
· Preferred habitat is branching, fernlike hydroid colonies.
· Cannot be cultured in quantities.
Collection Tips:
Large numbers of Caprellid skeleton shrimp colonize fouling growths and organisms such as sponges, tunicates, and especially large colonial hydroids such as Obelia (Rudloe, 1971). At some times of year, these sessile organisms will be alive with swarms of skeleton shrimp. The best way to collect them is thus to look for such fouling growths on man-made objects (docks, wharves, jetties, breakwaters, buoys, etc.) and harvest the sessile animals complete with all the Caprellids inhabiting them (Rudloe, 1977). (The skeleton shrimp attach themselves tightly to such growths with grasping hooks and they will cling tightly to the hydroid colony and come along for the ride when you carefully place it in your collecting bucket.)
Culture Instructions:
They cannot really be cultured in any numbers, but you might try placing a heavily colonized clump of hydroids or two in a refugium and hope for the best.

Skeleton shrimp are amphipods like Gammarus, but the Caprellids are very different in habits and appearance from Gammarids (The Caprellid, 2004). Whereas Gammarus are flat-bodied and seek shelter beneath vegetation and coral rubble, Caprella amphipods are thin and wiry (i.e., skeletal) and display themselves openly (The Caprellid, 2004). They have a long, slender thorax and almost no abdomen (The Caprellid, 2004). The spindly brown skeleton shrimp (Caprella acutifrons) are in constant slow motion, bending, stretching, somersaulting, and flexing languidly as they forage throughout the large hydroid colony they inhabit, gleaning diatoms from the stems and polyps and snatching up zooplankton (Rudloe, 1971). Thanks to their transparent bodies one can easily see the food particles streaming down their gut (The Caprellid, 2004). They owe their agility and acrobatic antics to the incredible flexibility of their slender, wire-like bodies and the fact that they have terminal hooks at their tail end and large grasping claws (gnathopods) like a praying mantis at the other end (Rudloe, 1971). Like a mantis, they often assume a prayerful attitude, slowly and reverently bobbing, then bowing their heads piously while clasping their "hands" together at their chests (Rudloe, 1971). They have two pairs of antennae and can turn their heads from side to side. Solemnly, they sway side to side, nodding and bowing down with great dignity.
Periodically they will interrupt their penitent meditation to begin actively foraging, and then they move altogether differently, with a unique method of locomotion that seems totally out of place in such clumsy looking creatures. Displaying surprising agility, they bend forward into a loop in order to get a good grip with their front claws. Then they swing their entire body over their heads, tail first, until their terminal hooks can grab a new hold, allowing them to release their grip with their claws and repeat the entire procedure (Rudloe, 1971). They are accomplished acrobats, advancing themselves end-over-end in a series of cartwheels and somersaults in this unorthodox manner. With the nimbleness and flexibility of a contortionist, skeleton shrimp can actually swing from limb to limb in this fashion (Rudloe, 1971), and it’s a comical sight to see them moving through the stems and branches and polyps of a bushy hydroid like a troop of drunken spider monkeys!
Thousands upon thousands of these tiny shrimp many inhabit a large clump of hydroids, and at first glance the entire hydroid colony appears to be writhing and crawling and pulsing with an eerie, unnatural life of its own (Rudloe, 1977). It is the tantalizing movement of these multitudes that apparently makes skeleton shrimp so irresistible to many fishes, and Jack Rudloe has often described how tossing a hydroid colony swarming with Caprellids into a seahorse tank will trigger a feeding frenzy worthy of a school of bloodthirsty sharks:
"Fish love to eat caprellid amphipods. Often we would tear off a clump of hydroids, toss it in the aquarium, and see even the most finicky reluctant feeders go wild and gobble up the tiny crustaceans as fast as they could pick them out of the hydroids. Sea horses especially love to eat them" ((Rudloe 1977, p100).

Pros (Giwojna, Oct. 1996):
· A highly nutritious, natural food for large seahorses.
· Available from bait shops or aquarium stores in some areas.
· Can be collected locally by many aquarists.
· Good tolerance for saltwater: marine grass shrimp are a "feed-and-forget" food and freshwater grass and river shrimp last surprisingly long as well.
Cons (Giwojna, Oct. 1996):
· Suitable only for the largest specimens.
· Cannot be cultured in home aquaria.
· Marine grass shrimp are unavailable to inland aquarists.
Collecting Tips:
Grass shrimp can be collected easily at low tide by vigorously shaking clumps of floating seaweed into a bucket of seawater, or by dragging a small seine or large aquarium net through tidal creeks or the grass flats just offshore (Giwojna, Oct. 1996). Similar techniques will often produce freshwater grass shrimp and river shrimp from freshwater streams or waterways (Giwojna, Oct. 1996). Remember, keep only shrimp that are small enough for your seahorses to swallow whole.
"Grass shrimp" is an all-purpose term loosely applied to several species of small marine shrimp as well as the young of a variety of larger shrimp (Giwojna, Oct. 1996). River shrimp are simply the freshwater equivalent of marine grass shrimp.
All in all, these crustaceans are ideal foods for the bigger breeds of seahorses. Just be sure to select shrimp of suitable size for your seahorses (Giwojna, Oct. 1996).
Seahorses are so fond of these shrimp that they often attack specimens that are far too big to swallow. They will attempt to break the back of the shrimp by snapping repeatedly at the carapace. If they are successful in severing the abdomen from the cephalothorax, the seahorses will then slurp up the tail section and head half of the shrimp separately. Or should their victim be so large it cannot even be swallowed in sections, they will snick out mouthfuls of the soft tissue exposed inside the abdomen or thorax. At times, several seahorses will gang up on one big shrimp this way, like a pack of lions teaming up to bring down a water buffalo that’s too big for any one of them to tackle alone. Under the right circumstances, a sort of slow-motion feeding frenzy may then ensue, with the seahorses playing tug-of-war over the pieces of their prize.
Grass shrimp that are too large to be overcome by such tactics may survive to become long-term residents of the seahorse tank, coexisting with their reluctant tankmates in a sort of uneasy truce. Such die-hard shrimp provide a useful service as scavengers from then on.

We tend to think of our seahorses as gentle, nonaggressive creatures that wouldn’t harm a fly, but in reality they are surprisingly fierce predators in their own right. To small crustaceans, seahorses are the tigers of the grassblade jungle, striking without warning from ambush and devouring anything of the right size that moves.

Best of luck supplementing your Sunburst diet with live shrimp you collect yourself, Haynes!

Happy Trails!
Pete Giwojna

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