Pete Giwojna

Dear Mr. Sherburn:

Wow, your question is much more involved than you realize, sir. There is no simple answer to your inquiry about how many of the babies from a brood can be expected to survive. That depends on the experience level of the breeder and the resources available to him or her.

For example, professional aquaculturists such as the folks at the Ocean Rider seahorse farm regularly achieve survival rates of well in excess of 90% of the fry for large tropical seahorses such as Mustangs and Sunbursts (Hippocampus erectus). On the other hand, inexperienced home hobbyists making their first attempt at rearing are very likely to lose the entire brood and a 0% survival rate is very typical for home breeders who are still learning the ropes…

Mustangs and Sunbursts (Hippocampus erectus) produce fry that are considered to be moderately easy to raise. The newborns are large enough at birth to accept newly hatched brine shrimp for their first food but they produce pelagic babies that go through an abbreviated planktonic stage, which complicates things just a bit. However, all things considered, H. erectus babies are among the fry with which home breeders have the most success, and more home hobbyists have closed the life cycle with this species than any other large seahorse.

There is always a steep learning curve when it comes to rearing newborn seahorses, and, as I mentioned, it’s quite common — perhaps even the rule — for the home breeder to lose the entire brood during his first few attempts at rearing. But as you refine your methods and become more proficient at providing suitable live foods for the newborns and work out the feeding regimen that’s most efficient for your particular circumstances, your results will get better. You will have more of the fry surviving for longer periods, until eventually you are able to raise a few of the fry from a few of the broods to maturity. That is a realistic goal for any home hobbyist working with Mustangs and Sunbursts who is willing to put in the necessary time and effort, which can be accomplished using a basic nursery tank and a staple diet of newly hatched brine shrimp.

In short, Dan, raising baby seahorses requires a tremendous commitment in time and resources, but rearing is only a burden that you need to assume if and when you feel you are up to the task.

As you know, sir, breeding in Hippocampus is often seasonal, regulated by cyclical changes in water temperature, day length, and salinity (monsoons). In the wild, both temperate and tropical seahorses breed best during the summer months and typically take a break from breeding during the offseason. For example, the breeding season for our native American H. erectus begins in April and lasts until the seahorses move into deep water with the onset of winter. Although domesticated seahorses that have been born and bred for aquarium life for generation after generation are no longer as strongly dependent on such environmental cues and will often breed year-round in captivity, even captive-bred seahorses sometimes experience a lull in the festivities at this time of year. That’s just their natural breeding cycle, the rhythm of life built into their genes.

So if you just don’t feel you are up to the challenge of raising baby seahorses at this point, Dan, it is relatively easy to prevent Mustangs and Sunbursts (H. erectus) from breeding by manipulating these environmental cues. If you don’t want your new seahorses to breed, just gradually reduce the water temperature to around 72°F and leave the aquarium light on for no more than 10 hours each day. In that case, the relatively cool water temperature and the reduced hours of daylight will affect the hormonal levels of the seahorses (especially the level of gonadotropin) and they will cease actively breeding, just as they do in the off-season.

If you want your seahorses to breed again, just gradually raise the water temperature (no more than 2°F daily) to around 77°F, and keep the aquarium light on for a least 12 hours each day, and the seahorses will respond to the increasing water temperature and day length with a renewed interest in courtship and breeding as these key hormones are reactivated.

So worrying about what to do if your first pair of seahorses produces a brood of babies before you feel you are ready to tackle rearing the young need not be your overriding concern at this time, Mr. Sherburn. You can easily turn off the breeding behavior in your seahorses if you wish.

When you feel you are ready for the challenge of rearing, you will need to set up a basic nursery tank for the babies as described by low, and prepare a battery of brine shrimp hatcheries in order to provide the newborns or juveniles with copious amounts of newly hatched brine shrimp (Artemia nauplii) on a daily basis.

The first task in preparing to raise seahorses is to set up a suitable nursery tank for the fry. Nursery tanks can be as simple and basic or as sophisticated and complex as the hobbyist prefers. Some home hobbyists find that Hippocampus erectus fry do well in the sort of basic nursery tank discussed below, but experienced home breeders usually achieve better results with a somewhat more elaborate nursery tank (e.g., a kriesel or pseudokreisel) designed for pelagic fry. First and foremost, the home breeder will need to decide what sort of nursery tank or tanks are best suited for his or her needs and interests.

Most nursery setups are bare bottom tanks that rely on twice daily (minimum) water changes to maintain optimum water quality. Siphoning the bottom at least twice a day is necessary due to the amazingly rapid production of fecal pellets the voracious fry generate, and a bare glass bottom facilitates the vacuuming process. The siphoning removes a small amount of water, which is replaced with freshly prepared saltwater, as discussed below. Simple air-operated sponge filters may be included to provide biological filtration, but that does not eliminate the need to make daily water changes while siphoning up the fecal pellets from the bottom.

Basic Nursery Tank

The simplest nursery tank setup is a bare bottom 5 to 10-gallon glass tank equipped with suitable hitching posts, an air-operated sponge or foam filter, and nothing else (Giwojna, Jan. 1997). Add a cartridge of activated carbon to the airlift tube of the sponge filter(s) to provide a little chemical filtration.

Keep the sponge filters in such nurseries elevated or prop them up off of the bottom. Otherwise they can become death traps for unwary benthic fry, which can become wedged beneath them and trapped. Adjust the airflow through the sponge so it produces a stream of medium-size, steady bubbles. You want to create a slow, gentle flow through the foam filter without generating overly fine or excessively large bubbles (Giwojna, Jan. 1997). Seahorse fry may accidentally ingest fine bubbles, mistaking them for food, while large bubbles can buffet the newborns with harmful results (Giwojna, Jan. 1997). Too much airflow through the sponge filters will leave them prone to "eating" the fry’s food (newly hatched Artemia, copepods, rotifers, etc.).

At the same time, however, you want the air stream to break up surface tension and provide adequate surface agitation. This is important not only for efficient oxygenation and gas exchange at the air/water interface, but also to allow the fry easy access to the surface. A newborn’s first instinct is to head to the surface to fill its swim bladder. (Physosymotous fishes have a connection between their gas bladder and the gut in the form of an open tube called the pneumatic duct, and are thus able to fill the swim bladder by gulping air at the surface. Like many teleost fishes, seahorses lose this connection very early in life, so that their swim bladders are completed closed as adults.) In many species, gulping air is the way in which gas is first introduced into the larvae’s bladder, and if denied an opportunity to do so, their development is hampered due to uninflated swim bladders (Silveira, 2000).

This is the case with seahorse fry. If denied access to the surface to inflate their swim bladders, the fry behave normally while they are small and their weight is still negligible. But over the weeks, as they grow and put on weight, their underdeveloped swim bladders and inability to achieve neutral buoyancy increasingly handicap them. Once they gain a little weight, they sink like rocks. Unable to swim, they are reduced to slithering along the bottom on their bellies and are commonly referred to as sliders. This deficiency does not become apparent until the fry are several weeks old. Needless to say, this hinders their swimming ability and severely limits their feeding opportunities, delaying their growth and development, and rendering entire broods useless. In several cases, the problem was traced back to an oily film on the surface of the nursery tank, which prevented the newborns from filling their swim bladders with air (Silveira, 2000). A protein skimmer will prevent this by removing filmy surface layers and surfactants in general.

The same sort of sponge filters that work well for dwarf seahorse tanks are also ideal for nursery tanks. Be sure to avoid sponge filters with weighted bottoms or other metal components since they will rust when exposed to saltwater. Sooner or later this will cause problems in a marine aquarium (sooner in the small nursery tanks). Select a sponge filter that has no metal parts and is safe for use in saltwater. The proper units will have suction cups to anchor them in place rather than a weighted bottom.

The sponge filters I find that work well are the Oxygen Plus Bio-Filters (models 2, 3, 4, or 5) or the Tetra Brilliant foam filters. They have no metal components, making them completely safe for use in saltwater, and just one of these foam filters will do the job on a tank of 5 gallons or less. They do not have a weighted bottom but are equipped with suction cups instead.

Click here: Foam Aquarium Filters: Oxygen Plus Bio-Filter 2

Avoid the Oxygen Plus Bio-filter 6, 11, and the Multi sponge, which all have a weighted bottom (metal), that rusts when exposed to saltwater. If you want more filtration, you’re better off going with two of the smaller suction cup sponge filters rather than any of the models with weighted bottoms. For instance, for a 10-20 gallon tank, I’d suggest using two small, well-established foam filters, one at either end of the tank for the biofiltration.

All you need to operate sponge or foam filters is an inexpensive, diaphragm-operated air pump (whatever is available at a reasonable price from your LFS will do just fine), a length of airline tubing to connect the air pump to the foam filter(s), and a set of air valves (gang valves) to regulate the air flow to the filters. That’s all — nothing to it! The inexpensive Apollo 5 air pumps work great for sponge filters, but whatever air pump you have on hand should certainly do the job.

Cleaning the foam filters is a snap. Simply immerse them in a bucket of saltwater and gently squeeze out the sponge until it’s clean and releases no more sediment or debris. (I use the saltwater I siphoned out of my aquarium when performing a water change for this, and clean my sponge filters whenever I change water.) Run a bottlebrush through the inside of the tube, wipe off the outside of the tube, and you’re done. The filter is ready to go back in the aquarium with no impairment at all of the biofiltration. Takes only a couple minutes.

Setting Up & Maintaining the Nursery.

The nursery tank(s) should be filled with water taken from the main tank that houses their parents, so the delicate newborns can be transferred directly to the nursery without adjusting to any stressful changes in pH, temperature or salinity (Giwojna, Jan. 1997). Cured ”seahorse trees” make good hitching posts, as do artificial aquarium decorations such as small seafans and soft plastic plants with fine, branching leaves (Giwojna, Jan. 1997). Strips, sections, and cylinders of plastic window screen or the plastic mesh sold in craft stores for needlepoint projects also work well. Short lengths of polypropylene rope (the kind sold at hardware stores and marine outlets for boating purposes) are another good option for hitching posts in the nursery. They come in many different colors, can be cut to any desired length, and are buoyant so if one end is anchored and the other end is unraveled, they will wave gently in the current like natural plants. (Avoid nylon rope, however — it bleeds in saltwater and will leech color and who knows what else into your tank!) If necessary, the holdfasts can be secured to the bare glass with silicone aquarium cement or suction cups designed for use in marine aquaria, or secured to a piece of coral rubble to anchor them in place.

Good lighting is also essential for the nursery tanks. The fry must be able to see the tiny organisms they live on clearly in order to feed efficiently. Use ”Daylight” fluorescent tubes or the equivalent and leave them on for a minimum of 14 hours a day, since the fry need to eat for at least 12-14 hours everyday (Vincent, 1995c).

Since the nursery tanks have limited filtration, daily water changes are needed in most systems to maintain water quality and keep up with the metabolic wastes and oxygen demands of several dozen baby sea horses and the thousands of brine shrimp needed to feed them (Giwojna, Jan. 1997). When the fry are well fed, defecation is amazingly rapid, with each newborn producing an average of one fecal pellet every 25-30 minutes (Herald and Rakowicz, 1951). The best way to perform the necessary maintenance is to use a length of airline tubing to siphon off the bottom of the nursery tanks a minimum of twice a day (morning and evening are ideal for this; Giwojna, Jan. 1997). Replace the water that was removed while siphoning with freshly mixed saltwater that has been pre-adjusted to the same temperature, pH and salinity as the rearing tank. Change about 10-20% of the water each time you siphon the bottom, so that a total of at least 25-50% of the water in the nursery tanks is exchanged every day (Giwojna, Jan. 1997).

The ocean rider seahorse training program includes lessons devoted specifically to breeding seahorses and raising the babies, Dan, and you will learn many more helpful tips for improving the survivorship of the when you get to those specific lessons.

Best wishes with all your fishes, sir!

Pete Giwojna, Ocean Rider Tech Support

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