Refugium setup and seahorse fry

Dear Lelia:

A refugium teeming with pods is certainly worth a try for anyone who is overwhelmed with broods of fry but nevertheless wants to give the newborns a chance, however slender that may be. The natural food of seahorse fry in the ocean is zooplankton, and research suggests that the bulk of this consists of larval copepods for many seahorse species.
The sort of simplified refugium-based rearing system you’re contemplating is similar to a "natural nursery," as described below, Lelia:

<Open quote>
The Natural Nursery.

This is a very small-scale, low-maintenance rearing system sometimes employed by harried home hobbyists who are too busy for the brutal feeding regimen and maintenance schedule most other nurseries require. Natural nurseries rely on lots of live rock for biofiltration and are usually set up more or less as a refugium would be. That means lots of macroalgae to provide natural filtration and no predators of any sort, which allows thriving populations of copepods, amphipods and other microfauna to build up over time. The idea is that the overworked aquarist can simply cull through his seahorse’s latest brood, release the hardiest of the newborns in the natural nursery, and allow them to fend for themselves. Sometimes a netful of newly hatched brine shrimp is added now and then to supplement the natural microfauna on which the fry survive, but this is done sporadically at best to stave off the appearance of hydroids and Aiptasia anemones that might otherwise rapidly take over the nursery. The natural filtration provided by the live rock and beds of macroalgae reduces the need for water changes to a minimum and feeding is drastically curtailed compared to other types of nurseries.

As you might expect, most of the fry are lost during the first week or two with this method, but some may manage to find enough natural fodder to survive and it’s not uncommon for a few of them to thrive on their own. That’s all the hobbyist is hoping for with this system and such meager survivorship is considered a victory, since the only alternative in many cases is to sacrifice the entire brood without attempting any rearing whatsoever.

This method of rearing is most successful when the natural nursery/refugium is large and the number of fry it is asked to support is small. For instance, Liisa Coit has used a 5-foot seagrass refugium this way quite successfully when rearing dwarf seahorses (Coit, pers. com.). It is best suited for raising benthic seahorse fry but is also worth a try for raising pelagic fry when there is no other alternative. <Close quote>

So attempting to rearing seahorse fry as you describe will result in very high mortalities, but it is far from hopeless, and it is not uncommon for one or two of the fry to hang in there against all odds and find enough natural fodder to grow and prosper. For example, Heather Hall maintained a rearing program for Hippocampus capensis at the London Zoo that was proving to be too successful, prompting a change in their rearing protocol. In order to keep from being overrun with captive-bred capensis, the Zoo was forced to resort to unusual methods to reduce the reproductive rate of their colony. She describes her experience raising these bountiful breeders as follows: "H. capensis is a relatively prolific species. Brood sizes average about 50 babies… Since survival rate is high with good husbandry and diet, it is easy to become overpopulated with animals. In order to avoid overpopulation we have tried different ways of managing the population in our collection. Separating the sexes was employed in several tanks. Sexes were kept isolated in groups of 20. We found that this led to many problems. The animals exhibited a number of stress signs: disease outbreaks increased and aggression was high between males. Females became swollen with eggs and suspected egg binding occurred. Respiration rates and twitching also increased. Therefore, we decided to separate the sexes of our seahorses no longer. Animals in the display tank are allowed to reproduce as normal, and young are only removed when required. Some young survive in the display tank, feeding on naturally available foods and make it to adulthood. To keep the generations turning over, we can remove up to 20 individuals and raise them in the holding tanks. They can be given special attention there and their growth monitored. This method has worked well for us" (Bull and Mitchell, 2002, p30).

In the end, H. capensis fry at the London Zoo were simply left to their own resources in the display tank with their parents, yet some of them routinely survived to adulthood on their own with no special care whatsoever. Those are benthic babies and the situation is a little different with Hippocampus erectus fry, but certainly worth a try, Lelia.

I don’t have any designs for the type of refugium you are planning, Lelia, but it seems quite feasible and should make an interesting project for a do-it-yourselfer. As an example, Charles Delbeek likes to use glass shrimp and cleaner shrimp that are too large to be eaten in the refugium for his seahorse tank, where the regular reproduction of these hermaphroditic crustaceans will provide a continuous supply of nutritious nauplii for his ponies: "There is a method that can be used to offer an occasional supply of live food for your sea horses. By setting up a separate system housing several species of shrimp such as the common cleaner shrimp (Lysmata amboinensis) or peppermint shrimp (lyse model wurdemanni), or Rhynchocinetes uritai or R. durbanensis, you can get a fairly regular supply of live shrimp larvae. These species are best to use since they can live in large groups and spawn on a regular basis. Such a system is commonly called a refugium. A refugium is a small (10-20 gallon) aquarium that contains live sand, live rock and/or macroalgae such as Caulerpa. It is plumbed such that water from your main system is pumped to the refugium and then returns via an overflow to the main tank. For this type of arrangement to work, the refugium must be slightly higher than the main tank. Shrimp are added to the refugium and within a few months they should start spawning and hatching eggs every few weeks. The larvae are then carried back to the main tank by the overflow, where they become a food source for your sea horses. Of course other life will also thrive in the refugium and it is not unusual for copepods, mysis and crab larvae to also be produced on a regular basis. The key to the refugium is to keep predators out of the system so that the smaller micro-crustacean population can thrive. You would need a fairly large and productive refugium to produce enough food to maintain even a pair of sea horses, so at best, a typical refugium can provide a nice source of supplemental live food; the basic daily diet still needs to be provided by you in the form of the frozen foods mentioned above." (Delbeek, November 2001, "Horse Forum," FAMA magazine)

Aside from the one Delbeek favors, refugia are available in a number of different designs. For example, there are easy-to-install external hang-on refugia and in-tank refugia as well as sump-style refugia that are mounted beneath the main. In the case of the latter, Barb, the refugium is installed exactly like any other sump. Here are a couple of online sites where you can look up more information on refugia, including articles explaining how to set up and install a refugium of your own:

Click here: Refugium Setups Information – From About Saltwater Aquariums

http://saltaquarium.about.com/od/refugiumsetups/

Click here: Refugiums

http://www.wetwebmedia.com/refugium.htm

Best of luck setting up a refugium-based nursery tank that will allow you to rear some of your seahorse fry with a little less effort on your behalf, Lelia!

Happy Trails!
Pete Giwojna

Dear Cheryl:

Yes, you’re quite right — if you can possibly provide them in suitable amounts, copepods are by far the best first foods for seahorse fry. Research shows that they are a natural prey item that constitutes a large proportion of the diet of pelagic seahorse fry in the wild. As such, the copepods are much easier for newborns to digest than newly-hatched brine shrimp, which have been removed from the marine environment by several million years of evolution. In addition, the copepods are much more nutritious with higher levels of highly unsaturated fatty acids and other lipids. Several studies demonstrate that seahorse fry grow faster and have improve survivorship when they are fed on copepods versus Artemia nauplii.

Best of all, research indicates that the newborns only need to be provided with copepods for about the first week of life (4-7 days) in order to achieve these benefits (Todd Gardner, pers. com.). After that, the newborns have grown enough and their digestive tracts have matured enough to be able to handle newly-hatched brine shrimp without difficulty and Artemia nauplii can serve as the staple diet for the fry thereafter.

In short, Cheryl, there is now considerable evidence that indicates copepods are a superior food source for newborn seahorses. In a nutshell, the copepods are simply far more nourishing and easier for the fry to digest than Artemia or rotifers.

For example, here are the abstracts from a couple of the recent studies on rearing seahorse fry with copepods that will give you a better idea of what I’m talking about (I would be happy to e-mail you copies of the complete studies off list if you’re interested):

Rearing West Australian seahorse, Hippocampus subelongatus, juveniles on copepod nauplii and enriched Artemia
M.F. Payne), R.J. Rippingale
School of EnÍironmental Biology Curtin University of Technology, GPO Box U1987,
Perth 6845, Western Australia
Received 3 November 1999; received in revised form 31 January 2000; accepted 31 January 2000

Abstract
Improved captive breeding techniques are required for seahorses. Artemia nauplii are generally considered a poor first feeding diet for many seahorse species. This study compared growth and survival of newborn Hippocampus subelongatus reared on cultured copepod nauplii and Artemia nauplii enriched with Super Selcow. Early growth and survival of seahorses were significantly greater when fed copepod nauplii. Copepod nauplii were well digested by juvenile seahorses whereas Artemia nauplii were not. Fatty acid requirements of seahorses could not be determined.

The addition of UV water sterilization improved seahorse survival. When offered copepod nauplii of different sizes, 5-day-old seahorses preferentially selected the largest nauplii. Maximum predation rate in these juveniles was 214 copepod nauplii/seahorse. Provision of copepod nauplii to juveniles improves the prospects of establishing captive breeding populations of H. subelongatus. q2000 Elsevier Science B.V. All rights reserved.
Keywords: Seahorse; Copepod; Artemia; First feeding; HUFA; Prey selection

And from Robin James, Weymouth Bioservices

Effect of copepod diet on growth rate of juvenile Hippocampus abdominalis.

Introduction:
Artemia is commonly fed to juvenile sea-horses as it is cheap and easy to culture. However, it is known to have a low nutritional value and is thought to be unsuitable for the delicate digestive systems of the juveniles. Copepods are smaller, more nutritious and less abrasive, but difficult to culture and more expensive than Artemia. This trial aims to asses whether a copepod enriched diet produces an improved growth rate of newborn H. abdominalis when compared to the growth rate produced by a standard Artemia diet.

This study produce much the same results — copepods proved to be more nutritious and resulted in faster growth and lower mortalities than newly-hatched brine shrimp. A number of other studies have since demonstrated the same thing.

So by all means, continue to provide a highly nutritious copepods for your newborn seahorse fry for the first several days of their lives if you can manage it. Once they make it past the first week of life, you can then switch them on to newly-hatched Artemia nauplii as their staple diet without any ill effects.

For best results, use only the freshly hatched Artemia nauplii which still have their yolk sacs largely intact. Such newly hatched brine shrimp will have good nutritional value and be small enough for the week old seahorse fry to easily swallow and digest. Here is a copy of Neil Garrick-Maidment’s article that describes one way of assuring the newly hatched brine shrimp you provide for the babies will have maximum nutritional value. (Neil is a very successful breeder in the UK and the author of two guidebooks on the care and keeping of seahorses.)

Rearing Seahorse Fry on Artemia.

Neil Garrick-Maidment

Director

The Seahorse Trust.

It has long been thought that rearing Seahorse fry on Artemia is impossible because they do not hold enough nutritional value. This is partially true but if dealt with in the correct way then artemia can be used very successfully.

Artemia is highly nutritious when it is first hatched out but the nutritional value drops very quickly to virtually nothing within 3 hours; added to this the carapace (shell) hardens during this 3 hour period and makes it very difficult to digest by all but the most harden fish fry.

The traditional way of cultivating artemia is to put the eggs into a pot of seawater, aerated at 80’ and wait for them to hatch 24 hours later. This one pot of artemia is usually used for a 24 hour period and quite often is stored in a refrigerator until it is used; this is where the nutritional problems occur unless the artemia is enriched. Once enriched (often for another 24 hours as the mouth parts do not form until 10 hours old) it often proves to be a poor source of food as it is by this point either too large or the carapace (shell ) of the artemia is too hard. By being too large or having too hard a carapace it means that fish fry like Seahorses cannot digest it as they have an extremely poor digestive system; which is not long enough to allow it to digest the hard carapace and derive enough nutrition from the naupilli. .

By changing the protocol of hatching the artemia it is possible to use it as a highly successful form of food especially for Seahorses; the only draw back with this system is that it is labour intensive.

The set up:

We use a 5 pot system for the hatchery, each one labelled 1 to 5; all five pots sit in a glass fish tank with 4 inches of water in it. This water is heated by heater/thermostat to 80’ and each of the pots is heated in turn by this hot water. Each pot also has an airline with an airstone into it.

The protocol:

Start with pot 1 and fill it with saltwater and add your artemia eggs (you can use unshelled eggs to increase the nutritional value higher.). 2 hours later repeat the process with pot 2 and then each 2 hours after repeat with the rest of the pots; it is possible to use more pots if your needs require it.

If you have set up pot 1 at 8am then 24 hours later at 8am the artemia should have just hatched out, this is then the time to feed pot one to your fry; it is crucial that the time between hatching out and feeding is kept to a minimum.

Harvest the artemia by letting the pot stand and the artemia will sink to the bottom and the egg shells will rise to the surface. Use a siphon through a very fine mesh trap to siphon them out of the pot, once you have enough artemia then give them a quick wash under a freshwater tap and then feed the artemia to your Seahorse fry.

It is crucial that you only feed a small amount of artemia to the Seahorse fry; enough to be eaten by the time the next pot is fed to the fry (2 hours later).

Once you have fed this pot of artemia to the fry do not be tempted to keep what’s left over, use it for some other fish species but don’t be tempted to feed it later on to the Seahorse fry.

Once you have harvested pot 1 immediately set it up again ready for the next 24 hour period.

Every time you go to feed the next pot of artemia be sure to siphon the tank of any debris from the bottom of the tank and crucially remove any left over artemia from the tank. This can be done by putting a light to the side of the tank to attract the artemia to it then siphon them from the tank. This is important as you do not want the Seahorse fry to be eating older hardened and nutritionally low value artemia.

After feeding the artemia remember to top up the water you have removed from the fry tank, this way you will be changing water throughout the day lessening the build up of harmful nitrites and ammonia in the water which is better for the Seahorse fry.

As a side note we usually use water from the adult’s tank to replace and indeed start up the fry tank; this is already filtered and as we use natural seawater it is a better source of water for the fry; they appear to do better in natural seawater than artificial.

These steps should be repeated every 2 hours with pots 2 then 3 then 4 then 5 and any others you add to the system.

This process should be repeated on time every 2 hours as the age of the artemia naupilli is important for its nutritional value and carapace hardness. <Close quote>

In short, Cheryl, I would suggest that you concentrate on feeding your newborns larval copepods for the first 4-7 days, and then switch them over unto newly hatched 1st instar Artemia nauplii, just as described by Neil above.

Best of luck with your prolific ponies and their offspring, Cheryl! Keep up the great work!

Happy Trails!
Pete Giwojna

Dear Cheryl:

Sure thing — I’ll be happy to send you copies of those references. You should have them by the time you are reading this post.

It sounds like you have worked out a very good feeding regimen for your newborn seahorses with the help of your son, and I hope your prolific ponies and their offspring continue to prosper.

Yep, I think a hang on refugium is worth a try, and if you can build up a sufficiently large population of copepods and larval shrimp, it may help increase growth rates and overall survivorship.

Best of luck with your seahorse population explosion, Cheryl!

Happy Trails!
Pete Giwojna