...for Marine Aquarium Cultured Fishes and Invertebrates
(Part 2 of a 2 part article)
by Dr. Amanda Vincent
University of Oxford, England
Article by Dr. Amanda Vincent,
Copyright 1995. Reproduced by permission.
(This article first appeared in Volume 3 Number 2, The Journal of MaquaCulture Spring
1995.)
| WEB Editors note: Dr. Vincent has granted permission for this reproduction with two conditions. 1. A reminder that this was generated from her "ROUGH NOTES" 2. These articles may be updated by Dr. Vincent or Dr. Heather Hall, at their discression |
Editor's note: Dr. Vincent kindly allowed Joyce Wilkerson to use excerpts from her "rough notes" for this article. This article is not to be reproduced without the permission of Dr. Amanda Vincent, Darwin Research Fellow, University of Oxford, Department of Zoology, South Parks Road, Oxford, OX1 3PS.
The first half of this article appeared in the previous issue of the Breeder's Registry newsletter.
Seahorse keeping should not be tackled by the casual aquarist, because seahorses usually die quickly in captivity. Seahorses are already at risk around the world, partly because they are exploited for aquarium fishes. The following notes are intended only for very experienced marine aquarists. Think about whether you can realistically hope to care for these fishes, before you buy them, and if you have any doubts, choose something easier.
Seahorses eat a great deal but are rather particular so feeding them is one of the most difficult aspects of keeping them. Seahorses eat live fresh food. They need a variety of foods and cannot be fed solely on an unbalanced diet of Artemia.
With patience and effort, you can convince seahorses to eat some frozen foods. However, frozen foods alone are not a balanced diet and will eventually result in malnutrition and illness.
Feed small amounts frequently rather than a lot at any one feeding. Twice a day feedings are probably adequate but three times a day is much better. Best feeding times seem to be as the full lights go on, and at mid-day, and again one to two hours before the main lights go off. If giving them live food, ensure they always have something to chase.
Seahorses are very poor competitors. They are ambush predators and wait until an interesting prey item appears - and then they use a powerful suction to draw it through their snouts. Some possible food options are:
A. Frozen Food
Frozen food is easy to use and sometimes highly acceptable to seahorses. Initially, introduce only a little frozen food at a time into a water current so the food seems to be alive - once one seahorse has started to eat, others follow.
1. Frozen mysids
* a favored food
2. Frozen gamma shrimp (only for big species)
* an excellent, nutritionally balanced food but seahorses don't
enjoy their hard shell.
3. Frozen Artemia
* seahorses aren't keen on this food - probably because
after freezing and thawing, there isn't much recognizable form.
* try to avoid using them.
B. Live foods
4. Artemia
* a very useful food although a bit tedious to rear and
expensive to buy.
* provide the stage (hence size) of nauplii most appropriate to
the size of seahorse.
5. Gammarids
* some seahorses go wild over these - particularly the larger
species.
* they hide and move suddenly so the seahorses get excited
watching for them - this may result in odd, worrying, postures as
the seahorses try to peer under rocks, etc.
* freshwater Gammarus are okay if the seahorses are keen on the
food.
* they last long enough in salt water to be eaten alive - some
seahorses will even eat dead Gammarus, so it's worth a try.
* marine Gammarus are very expensive to buy but can be obtained
on the coast.
* Gammarus can maintain a self-sustaining colony. Put some into
the coral gravel of a tank and leave them alone. They feed on the
algae and reproduce and grow well, although the culture may have
to be restarted from time to time.
6. Baby guppies and mollies etc.
* Seahorses vary in their response to these but sometimes they
get wildly excited - especially the larger species.
* Use new born fish and only place a few in the tank as fresh
water fish die quickly in salt water.
7. Plankton
* If you live on the coast, get a fine mesh plankton net to catch
wild plankton.
* Plankton is probably particularly important for brooding males.
8. River shrimp
* Available locally or from aquarium shops (very expensive).
* Give size appropriate shrimp to seahorses.
9. Daphnia
* Available from ponds in summer.
* Seahorses are not usually very interested in them and only take
the larger ones.
* There is a danger of Daphnia fouling the tank because the
Daphnia die quickly in salt water.
10. Tubifex, chironomid larvae etc.
* Basically ignored by seahorses.
Artemia eggs are available from aquarium shops. They are expensive but you can set up a self-perpetuating colony where Artemia breed more Artemia for you. Here's a simple way of culturing Artemia:
Artemia take about fourteen days to reach maturity, after which they produce their own eggs. It's better to have several containers going simultaneously and to take a little from each. Artemia can be reared more simply in the summer by starting an algae culture in a tank outside with plenty of sunlight and adding Artemia adults and nauplii to the mature algae culture and they will culture themselves - however, addition of yeast from time to time seems to help.
We know that the "pregnant" seahorse is really a male because male seahorses, like all other male animals, produce sperm whereas female seahorses produce eggs.
The seahorse courtship is lengthy (requiring 3 mornings), active and colorful. Courtship is similar across species. Shortly after dawn, the male and female come together, the male inflates his pouch with water, and both sexes signal their interest in courtship by brightening significantly. Both seahorses grasp the same holdfast with their tails and begin to circle like merry-go-round horses. At frequent intervals, they release the holdfast and make their way, in tight parallel formation, across the bottom to another holdfast.
The male bends vigorously, jackknifing his tail to meet his trunk, thus compressing the pouch. This motion pumps water in and out of the pouch and closely resembles the motion to release the young at birth.
On the third morning of courtship, the female's trunk becomes rounded, as she ripens the eggs in her ovary, and her ovipositor begins to protrude. When she is ready to transfer eggs, she releases the holdfast and stretches upward - "points" - as if to rise to the surface, keeping her tail tip on the ground. Eventually the male responds to the female's pointing, and together they rise through the water. As they ascend, the seahorses face one another with their tails bent back, and the female inserts her ovipositor into the open pouch of the male and releases her eggs in a long sticky string. To transfer the whole clutch takes only about six seconds and then the pouch opening is sealed shut. The pair breaks apart and the male gently sways to settle the eggs in the pouch while both settle down on the bottom with their tails wrapped around holdfasts.
Females play no role in parental care. Eggs are fertilized in the pouch. The developing embryos are aerated, osmoregulated, and nourished in the pouch. The hormone prolactin initiates enzymatic production of a marsupial fluid which nourishes the young in the pouch.
After a pregnancy lasting several weeks (depending on the species), males go through a difficult "labor", lasting up to 2 days. At hatching, the young are well developed and independent and receive no further parental care. Males remate within hours of giving birth.
Seahorses are monogamously pair-bonded. In Hippocampus fuscus and H. whitei, one male and one female mate repeatedly and exclusively. Pair bonding is reinforced by daily greetings, performed exclusively with an individual's partner: each pair of seahorses comes together every morning, changes color and performs the first few movements of courtship. If a male and a female have been together for a long time (more than half a pregnancy) before mating, the male gives birth to significantly more young, probably because the male is somehow stimulated by the female's presence to increase his pouch capacity or his production of hormones important in incubation, such as prolactin.
If a male has given birth, check the tank thoroughly for young. They will normally be born in the early morning and almost certainly before noon. If a male bends and thrusts as if giving birth, but no young are released, he is almost certainly going through courtship behaviors, even if no female is present.
The table below offers a rough indication of the young number and size:
| SPECIES | NUMBER | SIZE (cm) |
| H. reidi | 300-1500 | 0.6-0.8 |
| H. kuda/comes | 150-500 | 0.6-1.0 |
| H. erectus | 100-800 | 0.8-1.3 |
| H. histrix | 100-300 | 0.7-1.1 |
| H. fuscus | 10-100 | 0.8-1.2 |
| H. zosterae | 10-50 | 0.6-0.8 |
It is easier to rear larger young, which is not necessarily a species with larger adult size.
Young usually swim to the surface for the first few hours
after birth to fill their air bladders, after which they disperse
into the corners of the tank.
DO NOT EVER REMOVE A BABY SEAHORSE FROM WATER.
They will gulp air and be unable to submerge.
Young seahorses grow rapidly and triple in size in 3-4 weeks. Most young reproduce in about a year.
When the young are very small, there should be no filtration in the tank. Ensure that a water change of at least 10% is carried out every day. Initially young should be in the same water as the father's tank (from where they came) but it is best to adjust the temperature to 26C C (78-80 F).
Hydroids and miniature jellyfish polyps, if present in the rearing tank, can kill the young seahorses by stinging. Wipe the sides of the tanks with a sponge to remove them. Also, remove rocks and keep long filamentous algae out of the tank as young can get caught.
The young need 14-17 hours of light daily and feeding periods must extend over at least 14 hours daily. Use small bubble aeration as large bubbles may destroy young seahorses. If possible, keep broad leafed Caulerpa algae with young to take out nitrites. Darken the back walls of the tank because these are often brighter and babies collect there and forget to feed. Ensure that the young have sufficient holdfasts - such as thin tubing or narrow plants.
For young born greater than 1.0 cm (0.4"), newly hatched Artemia nauplii are a basic food which should be supplemented by other plankton. Artemia nauplii seem to allow growth and survival for at least six weeks. After that, the food source may be too imbalanced. The Wilhelmer Aquarium has found that seahorses don't flourish on Artemia alone, partly because the young seahorses find Artemia difficult to digest.
The young should never be totally without Artemia nauplii. Avoid brine shrimp shells as these are sharp and can kill young seahorses. At first, two liters of Artemia hatchlings in water may suffice but the young seahorses will soon require that amount three times a day.
A more reliable way to feed seahorse young is more complicated but the Berlin Aquarium manages about 85% survival this way, with the help of a full-time technician!
You need:
1. To culture algae: Set up a tank with double salinity saltwater to prevent growth of plankton. Then add Dunaliella algae. A starter culture can be obtain commercially (Florida Aqua Farms, Dade City, Florida) or you may be lucky enough to get it from a public aquarium or botanical institute. Then, for each 70 liters of algae culture, add 5 ml Wuxal plant fertilizer weekly -- roughly 1 ml of fertilizer per 4 gallons of culture. (Wuxal is similar to Microalgae Grow� from Florida Aqua Farms). Maintain the culture in constant light (normal white) with aeration. Clean the tanks regularly. It is safer to have at least two algae tanks going at once; one which is developing and one from which you take algae to feed plankton. It takes about 1-2 weeks to grow algae. When the algae tanks are dark green, then transfer algae water to the zooplankton tank.
2. To feed the algae to zooplankton: To start the culture, buy plankton or use water from the ocean or in which fish are imported as a starter. The tank should be lit 24 hours a day with white light. Use the same salinity water as for the young seahorses. The algae water will have to be mixed with fresh water to dilute it. Add more algae to the plankton tank whenever the water is clear. Take any accumulated sediment on the bottom of the plankton tank out before feeding the zooplankton with more algae, strain it and feed it to the zooplankton again. Add about 7 liters of algae for each 50 liters of zooplankton (roughly 1.5 gallons of algae per 10 gallons of zooplankton) every ten days or so. Retain enough algae culture to restart a new algae culture.
3. To feed zooplankton to baby seahorses: Young seahorses don't need to be feed the first day after birth. After that, use two plankton nets of zooplankton 5-7 times daily (whenever no plankton is visible in the rearing tank) AND have a drip of diluted plankton going at a rate of 10 liters per 24 hours. The drip can be from a bucket on top of the tank with an airhose siphon (with valve controlling flow).
4. Switch to Artemia After 10 days to 2 weeks, start the young on Artemia nauplii Give them about 5 nauplii per seahorse per feeding and scatter them widely rather than clumping them. You can also give them small Daphnia as they grow. Keep feeding the young with zooplankton as well for about 3-4 weeks. Feed 5-7 times daily for about 6 months until the young are 4 cm (1.5") long.
Please send any of your own advice and suggestions on keeping seahorses to Neil Garrick-Maidment, Seahorse Captive Breeding Co-ordinator, 1 St. James Terrace, Exeter, Devon EX4 6HQ, England. He is working with Dr. Vincent to establish a central register of serious seahorse keepers and a directory of breeding and rearing information, in order to assist in conservation efforts.
Part 1 of this article is available HERE