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Nutrition Part IV: Feeding & Rearing the Fry
by Pete Giwojna
from the December 1996 issue of Freshwater and Marine Aquarium magazine (FAMA)
In the last issue of FAMA ("Sea Horse Nutrition, Part II: Frozen Foods for Adults"), you learned how to train Hippocampids to accept a variety of frozen foods. Now that your sea horses are used to eating nonliving food, you're ready for the most rewarding method of providing these fascinating fish with a balanced diet--feeding them by hand!
Handfeeding sea horses has several important advantages for both the aquarist and his pampered pets. First of all, it breaks the sea horse's dependency on live foods, allowing the hobbyist to offer them a wide assortment of nutritious foods that would otherwise have to be excluded from their diet. Unlike live foods and frozen fare, which are limited to prey that is small enough to be swallowed whole, the food that is used for handfeeding can be cut into convenient, bite-sized pieces. Therefore, just about any type of fresh or frozen seafood that can be obtained at an aquarium shop, pet store, grocery store, fish market or bait shop can be used for handfeeding, which makes it much easier to provide a healthy diet for your sea horses.
Secondly, feeding your sea horses by hand makes it easy to regulate how much each of them eats on a daily basis. There always seems to be at least one shy, subordinate fish in every aquarium that never gets its fair share at mealtime. When handfeeding, however, the aquarist himself determines the amount each of his fish gets, so none of them ever go hungry. This makes it possible to keep sea horses in a community tank with more active fishes that would ordinarily out-compete them for food2, since the aquarist can personally deliver each mouthful to the sea horses while keeping more aggressive specimens at bay.
Likewise, handfeeding sea horses allows them to be kept in aquaria with stronger currents than would otherwise be possible. Hippocampids are very deliberate feeders: they must single out individual prey items, carefully track their intended victim until it closes within a few millimeters, and then suck it up using their tubular mouths like miniature slurp guns. Consequently, when swirling currents whisk their prey past them too quickly, sea horses have great difficulty targeting and tracking separate food items, and their normal feeding habits are disrupted. These slow-moving fish can have a very hard time getting enough to eat under such circumstances. Handfeeding circumvents this problem, and is thus ideal for sea horses in reef tanks and other systems where strong circulation and vigorous water movement are required.
More importantly, feeding your sea horses by hand permits the aquarist to conduct a close-up, daily inspection of every specimen in his tank. These detailed examinations make it difficult not to notice any subtle changes in your sea horse's appearance or behavior that might signal impending problems with disease or the water chemistry. That's a big advantage, since the sooner such potential problems are detected, the easier they are to cure or prevent.
Last but not least, handfeeding is pure, sure-fire, 100% unadulterated fish-keeping fun! Having your pet ponies literally eating out your hand is a very rewarding experience. When one of these shy, enchanting creatures--whose very survival in the wild depends on concealing itself from predators at all times--comes trustingly up to the surface to take food right from between your fingers, it's a thrill you won't soon forget. The training sessions and daily feedings required by this technique tends to forge a close, personal relationship between the aquarist and his charges, and hand-fed sea horses often become special pets. They have excellent vision and soon learn to recognize their keeper, often swimming to their feeding station at the front of the aquarium whenever the aquarist approaches, begging for a handout.
In short, this is the perfect technique for feeding sea horses in the mini-reef or community tank. It helps the aquarist prevent disease and malnutrition, and makes sea horse-keeping a real joy. As a result, your sea horses' chances of living a long, healthy life improve greatly if you can train them to accept handfeeding, and the following step-by-step instructions will explain exactly how this can be done.
Training sea horses to eat from your fingers is basically a gradual process of behavior modification (Sprung, 1994). It proceeds through a series of orderly stages, and the aquarist uses tasty treats as rewards to shape the sea horse's behavior at each step in the process3, as described below:
(1) Sea Horse learns to eat carefully-selected, nonliving prey and frozen foods;
(2) Sea Horse learns to associate the feeding tube with the presence of these tasty nonliving tidbits;
(3) Sea Horse learns to follow tube to a feeding station near the surface of the water before receiving his reward;
(4) Conditioned by these rewards, sea horse becomes accustomed to eating in close proximity to the aquarist's hand, as it is gradually moved closer and closer to the end of the feeding tube;
(5) Sea Horse learns to take food directly from your fingertips, without the feeding tube.
The easiest way to get sea horses used to eating nonliving prey or frozen food is to offer them their favorite live food (grass shrimp, Mysids, newborn guppies or mollies, etc.) after it has been freshly killed. As described in the last issue of FAMA, the freshly dead or frozen morsel must then be presented to them so that it still appears to be very much alive. (If you have not already accomplished this step, refer back to "Sea Horse Nutrition Part II: Frozen Foods for Adults" for more suggestions on how to impart the necessary movement to such nonliving food items.)
Your next step is to get the sea horse to accept the same frozen foods from the end of the feeding tube (Sprung, 1990). This device is simply a 24-inch length of rigid, 3/16"diameter airline tubing to which an equal length of flexible airline tubing has been attached2. The flexible tubing allows it to be used as a sort of pipette, so a bite-sized tidbit can be sucked up and positioned at the very tip of the tube for easy feeding.
The feeding tube can then be used to manipulate this frozen morsel so the "prey" seems to be moving or swimming in a lifelike manner. Just place the morsel within the sea horse's view and let it drop so it drifts down lazily right in front him. If he doesn't grab it on the first pass, pick it up again with the feeder and repeat the maneuver as often as necessary. Or you can use the tube to hold the morsel within easy reach of the hungry sea horse, waving it tantalizing before its very nose until it can no longer resist snapping it up. Either way, move slowly and be careful never to touch the sea horse with the feeder--there's a fine line between tempting the timid creature and alarming it. (You'll quickly discover the feeding tube is also indispensable for tapping away pesky fish and invertebrates that threaten to disrupt the lesson2. In fact, it's a good idea to feed the more aggressive tankmates right before you begin your sea horse's training sessions.)
It's also advisable to conduct your lessons at one particular place in the aquarium. Select a quiet, unobstructed area near the front of the tank with a convenient hitching post close by, and feed the sea horse at the same location every day. Before long, a clever sea horse while begin to anticipate these feeding sessions and swim straight to this spot as soon as the aquarist approaches 2.
After following this routine for 7-10 days, the sea horse will have formed a strong association between the tube and its food (Sprung, 1994). You can now use the feeder to lure the sea horse to the surface of the tank--where handfeeding can more easily be conducted--by holding the tip of the tube just out of its reach and making the sea horse follow it up to the top in order to receive its reward. At the same time, begin moving your hand a little closer to the end of the tube eat time you use it, so the sea horse gradually gets used to seeing your fingers nearby while it eats. Shorten the distance between your hand and the end of the feeding tube a few inches each day, and when there's only a short gap remaining, you're ready for the final step: Present the reward at the end of the tube as usual, but before the sea horse eats it, remove the shrimp and offer it to him from your fingers instead2. Use two of your fingers like a tweezers to remove the piece of shrimp and hold it out for the hungry 'horse.
Julian Sprung was the first to perfect this conditioning process and write about handfeeding2. He advises that sea horses usually make the transition from feeding tube-to-fingers quite smoothly, but at first it may be necessary to drop the piece of food while the sea horse is looking, until it finally realizes that the food--which momentarily disappeared between your fingers--is still right there, waiting to be eaten. He says it takes a little practice to get used to holding the slippery morsel between thumb and index finger so that most of it protrudes in plain view without dropping it in the process2. Once you get the hang of it, it doesn't take long for the sea horse to learn it can safely approach your hand and take food from your fingers, and when one sea horses learns to do so, others will often follow its lead. From then on, handfeeding is easy--providing you feed the more active specimens first.
What frozen foods make the best rewards when conditioning sea horses to accept handfeeding? Julian Sprung recommends using grass shrimp (freshwater or marine) for these training sessions, since it is a favorite natural food of sea horses and is often sold in pet shops along with feeder fish2. He finds that the last segment of a freshly-killed or frozen grass shrimp, which includes the telson or tail, is ideal for this: it is small enough to be swallowed in one piece, yet with the tail attached it looks just like a small, intact shrimp. The visual stimulus of the shrimplike tail section as it drifts lazily past, combined with the olfactory stimulation provided by the tempting scent of its bodily juices, is just the right recipe for attracting a hungry sea horse's interest. When he cannot obtain grass shrimp, Sprung uses a single swimmeret from an edible shrimp in its place2. (I have had the best luck using frozen Mysis shrimp during my handfeeding lessons. They are small enough for the entire shrimp to be used, making them even more lifelike, and sea horses really love them.)
The expensive grass shrimp are used only during the initial training period. Once his sea horses are accustomed to handfeeding, Sprung switches to bite-sized pieces of frozen shrimp from the supermarket as their basic diet2.
Bill Thompson, President of the Sea Horse Hobbyist Society, has mastered a similar hand-feeding technique that eliminates the need for a feeding tube4. He finds that sea horses will often be drawn to your hand by the scent of the food, and can usually be persuaded to nibble on it when it is gently waved under their noses. Just hold the chopped shrimp between your fingers, keep still, and let the mouth-watering aroma draw the sea horse to you. He suggests "taming" the sea horse first by gently petting or stroking its flanks from time to time4. (Despite their "armor-plating," sea horses seem to enjoy tactile stimulation, and will sometimes bask in the stream of bubbles from a airstone for that reason.) He stresses the fact that your hand must be moved in a slow, non-threatening manner at all times, and that the aquarist must never press the matter if the sea horse appears to be getting "spooked" at any point in the taming or training process. If you persist, it will only heighten the sea horse's sense of distress, and the unpleasant experience will make it reluctant to accept further training.
(I agree that Thompson's shortcut is an effective training technique that can significantly shorten the conditioning process, if you really know what you're doing. If not, it's all too easy to bungle your first attempts, stress the sea horse, and end up teaching it the wrong lesson--to associate your presence with fear or danger, rather than food. Thereafter, it will regard your hand as a "negative stimulus"--a dangerous intruder to be avoided at all costs--and you could wind up with an untrainable sea horse. Thus, if you're a beginner, I'd recommend using Sprung's tried-and-true training methods and starting out from scratch with the feeding tube. It'll take a little longer, but it's a lot less risky. After you've successfully trained a sea horse or two, you can confidently try Bill Thompson's shortcut to handfeeding.)
Thompson also cautions that the tidbits used for handfeeding must be of suitable size--no bigger than 1/8" or about the size of a grain of rice--and should consist of the sea horse's favorite food4. He warns against overfeeding and advises that any uneaten food must be promptly removed. For the average sea horse, 6-7 morsels the size of a grain of rice should suffice for a single feeding session. There should be two or three of these feedings spread out over the course of the day, bearing in mind that if one of your sea-going gluttons eats too much at one sitting, it will regurgitate most of it later on2.
CAUTION: Before the aquarist places his hands or fingers in the aquarium, they must be cleansed thoroughly. Always remember, even so much as a residue of handsoap left beneath a fingernail may be enough to poison your entire tank. The best way to avoid such problems when handfeeding is to use a quality, antibacterial liquid soap beforehand and then rinse well with hot water. When you feel your hands are clean, repeat the rinse a second time to make absolutely certain no lingering traces of soap remain.
Ordinarily, you can expect the conditioning process to take a week or two to complete. However, to a large extent, intelligence determines how quickly the training proceeds, and some sea horses are just plain smarter than others. Sorry fellas, but when it comes to "horse sense," it seems the fairer sex got the bulk of the brains as well as the beauty. The more stupid stallions are sometimes hopelessly baffled by reflections on the aquarium glass and the surface of the water, to the point that they can't tell which is the real food and which is merely a mirror image. Evidently the more gifted fillies have no trouble seeing right through such illusions, and Julian Sprung reports they often learn his handfeeding technique much faster than the males (1994, personal communication). (Not such a good "reflection" on the male gender, in general, is it?)
My own hand-feeding experience tends to confirm Mr. Sprung's observation that females sea horses are often easier to condition. But as a red-blooded American male who has no trouble telling whose throat he's cutting in the mirror while shaving each morning, I dislike the theory that merely possessing a Y-chromosome automatically makes mental midgets out of the male of the species.
I prefer to think the difference in the training ability of the sexes is due more to biology than intelligence per se. In the wild, male sea horses are nearly always carrying eggs or developing young and, out of protectiveness toward their brood, they may thus naturally be more cautious and reticent than their mates when suddenly confronted with new, potentially dangerous situations (such as a clumsily-executed handfeeding lesson).
Or it's possible that males are simply more visually-oriented whereas females have a better sense of smell and therefore tend to follow their noses more. Hence the stallions are easily misled by optical illusions while the mares merely follow the scent of the food straight back to its source. Single males are known to wander widely in search of a mate5, and they may need to rely more on their vision both to avoid predators and to locate any available females when exploring new territory. Females, on the other hand, may depend more on their sense of smell, since there is some evidence that they are stimulated chemically when the males "pump" their empty-but-fully-inflated pouches5 in the female's direction during courtship. This vigorous pumping action wafts brood chemicals from their pouch toward the female--chemicals which some researchers believe may actually stimulate ovulation and trigger mating5.
Or maybe it's just that the fillies rely on female intuition to guide them unerringly to the goodies.
Whatever the reason, not all sea horses can be conditioned to accept handfeeding. Some of the slow learners never catch on. Besides intelligence, personality also plays a role. Some individuals are just too nervous and edgy to ever become comfortable with this unorthodox method of feeding. Others are too stubborn and set in their ways--their behavior too rigid to adapt to handfeeding. And others are ruined by a clumsy, premature attempt at handfeeding, which rendered them unreceptive toward further training. But with care and patience, most sea horses eventually learn to enjoy being fed by hand.
Once they get used to handfeeding, it's important to tantalize your sea horses with a good selection of choice "finger foods." If they are fed the same old thing day after day, they tend to lose interest in frozen foods after a few weeks. They can be finicky feeders under the best of circumstances, and their appetites often suffer when they are given a steady diet of nonliving "prey." They will begin to eat half-heartedly and, if the aquarist fails to respond, they will eventually stop eating altogether--a scenario that can lead to malnutrition, illness, and ultimately death. (After all, no matter how wonderful it tastes at first, a steady diet of fillet mignon, caviar, and chocolate mousse would become both unhealthy and unappetizing before long, and you'd be begging for something different after a couple of weeks.)
To prevent this from happening, change your sea horses' menu from time to time. At the first sign of disinterest, try tempting them with something new. There's no point trying to force them to eat something they no longer like, no matter how nutritious it is. I mean, speaking from personal experience, a guy can eat only so much oat bran, wheat germ and bean sprouts before his stomach rebels. Sea Horses are much the same: frozen fare may be good for them, but nonliving foods don't excite their interest, and they tire of it quickly.
To combat this problem, I recommend offering your pet sea horses a wide selection of fresh, frozen, and reconstituted freeze-died treats when handfeeding. This should include plankton, krill, prawns, and shrimp of all kinds (Mysids, grass, glass, Gamma, ghost, pink, edible, etc.). Although hard-bodied crustaceans such as these are best and should constitute the bulk of your sea horses' diet, just about any seafood that can be cut up into bite-sized pieces is worth trying as an occasional treat. Crustaceans and seafood that are too large to be swallowed whole must be carefully chopped or diced into tempting tidbits no bigger than 1/8" across. While thawing, they can be soaked in good liquid vitamin preparation or a special food additive such as Selcon Concentrate to increase their nutritional content.
Use your imagination--if your bait shop has crayfish, try feeding them rice-sized bits of meat from beneath the tail or claws (frozen crawdad keeps a long time, and if they like it, one crawfish can provide many meals). Or you might consider offering them slivers of frozen clam, squid or scallop from the pet store--or the seafood section of your supermarket--or perhaps even bits of fresh fillet from the local fish market. Don't be afraid to experiment--your sea horses will let you know in no uncertain terms whether or not such occasional delicacies are to their liking.
But no matter how varied the menu or how enticingly the hand-picked delicacies are served up, sooner or later your sea-going gourmets will still grow tired of frozen cuisine. The best way to prevent a hunger strike when handfeeding is to supplement your sea horses' staple diet of frozen fodder with regular feedings of live foods.
Proven favorites that are guaranteed to tickle the most fickle filly's fancy are live Mysis shrimp, grass shrimp, zooplankton, and adult brine shrimp. Gammarus amphipods are likewise relished by most large sea horses, and newborn guppies, mollies and other livebearer fry are also worth a try. Some sea horses refuse to eat baby fishes--others go crazy over them. (See ''Sea Horse Nutrition, Part I: Live Foods for Adults'' for more information on collecting and culturing live foods.)
But the type of live food you provide isn't nearly as important as the fact that it's genuine, living, struggling prey. The erratic movements of such natural prey items trigger a sea horse's feeding response and stimulate its appetite. As a result, nothing ends a hunger strike quicker than a serving of the live foods that all sea horses instinctively crave.
In short, your goal should be to handfeed your pampered ponies a wide range of fresh and frozen foods that have been fortified with special food additives such as Selcon as their staple diet. This basic, everyday diet should then be supplemented with liberal amounts of live foods as often as possible. Frozen foods alone cannot meet your sea horses nutritional requirements, and occasional feedings of living prey will keep them eating and further round out their diet.
Following this recommended feeding regimen will assure that your sea horses receive a balanced, nutritional diet at all times. They will respond with renewed health and vigor, and you can expect well-fed adults to pair up and demonstrate a healthy interest in breeding.
In fact, sea horses breed more readily in captivity than any other marine fishes, and the next article in our series on ''Sea Horse Nutrition'' will be devoted to rearing their fry. The special techniques it discusses will give dedicated hobbyists a reasonable chance to raise sea horses at home.
Author's Note: If you are a beginner who is considering keeping sea horses for the first time, remember that furnishing these fascinating fish with a healthy, balanced diet is a painstaking, time-consuming process. It requires collecting live foods in the field, maintaining live food cultures at home, patiently training them to eat nonliving prey and frozen foods, and even conditioning them to accept handfeeding, as described in this segment. Anyone who is unwilling or unable to follow the feeding procedures outlined in these articles should stick to less demanding fishes that are suitable for the novice.
If you decide you're up to the task, be sure to make provisions for feeding your sea horses before you buy them. Sea Horses must NEVER be purchased on impulse! It's vital that you line up live food sources or establish your own live food cultures before you bring them home. And keep in mind that it will be much easier to keep up with the bottomless appetites of these seagoing gluttons if you keep them singly or in pairs.
When selecting a sea horse, always try to obtain a fully mature adult of the species you desire. Adults are generally easier to handfeed and, as Dr. Amanda Vincent has pointed out7, in the interests of sea horse conservation, juveniles should be left in the ocean until they have had a chance to reach adulthood and reproduce. Fewer immature specimens would be removed from the wild if hobbyists everywhere refused to buy subadults, and sea horse populations around the world would benefit as a result.
(1) Giwojna, Pete. 1990. A Step-By-Step Book About Sea Horses. T.F.H. Publications, Inc.: Neptune City, New Jersey.
(2) Sprung, Julian. 1990. Hand fed horses. Freshwater and Marine Aquarium: 74-75.
(3) Sprung, Julian. 1994. Two Little Fishes, Inc. 4016 El Prado Boulevard. Coconut Grove, Florida 33133. (Personal communication.)
(4) Thompson, Bill. 1990. Sea Horse Hobbyist. 2821 Hollins Ferry Road; Baltimore, Maryland 21230. (Personal communication.)
(5) Vincent, A.C.J. 1990. Reproductive Ecology of Sea Horses. Ph.D. Thesis, University of Cambridge: 15, 61.
(6) Vincent, Amanda, Ph.D.. 1995. Sea Horse keeping: feeding adults, mating, rearing the young, mariculture. The Breeder's Registry . Volume 3, Number 2: 1-5.
(7) Vincent, Amanda, Ph.D.. 1995. Update on sea horses. SeaScope (Summer '95) 12: 4.