Breeding Dwarf Seahorses

Expert tips on propagating the CITES listed Hippocampus zosterae.

People have held seahorses in awe for millennia, though they are often not sure what to make of these amazing creatures. Seahorses have eyes like a chameleon that can move independently of one another, an exoskeleton like an insect, a pouch like a kangaroo and a grasping tail like a monkey. They can change color, seemingly float through the water by some mysterious form of propulsion (they have almost invisible fins), and it is the males that give birth to live young. Even scientists weren’t entirely sure what to make of them, so seahorses were considered to be aquatic insects well into the 1800s.

Zosterae Background
The dwarf seahorse (Hippocampus zosterae), along with the entire Hippocampus genus, has been listed on CITES (Convention on International Trade in Endangered Species) since May of 2005. Due to extreme commercial (not the aquarium industry) pressure on a few species, this unprecedented action was taken without any population research on the various species. Today the International Union for the Conservation of Nature (IUCN) Red List considers H. zosterae as “data-deficient,” meaning that no one has really looked into the dwarf seahorse’s population dynamics.

Even though dwarf seahorses are listed on CITES, CITES only controls international trade. (See the “Seahorses and CITES” sidebar for more information.) And because these seahorses are common in Florida, nothing more than a fishing permit is required to collect them, and there are no regulations regarding interstate transport or possession within the United States. I’ve talked to several collectors who gather wild dwarfs for sale and several hobbyists who occasionally collect them for their own use, and they all report that wherever there are eelgrass beds in the range of H. zosterae, dwarfs are plentiful. Collectors can gather all they want in just a few minutes of fishing. According to these anecdotal accounts, dwarfs are widespread, and their populations appear stable.

Acquiring Dwarfs
There are several ways you can acquire dwarf seahorses:


  • Local fish store. Many local marine stores can order a pair of dwarfs for you if they buy fish from Florida.
  • Mail order. The company that used to advertise in comic books is still around, as are many others.
  • Online vendors. Several online vendors have been farming or collecting and selling wild dwarfs for decades. All of these vendors ship healthy fish and have been doing it for a long time.
  • Online auction sites. You can also find dwarfs online at various auction sites. Just be sure that the seller has good feedback and knows what he or she is doing.
  • Local fish clubs. Several years ago, I was able to get a couple pairs from a fellow member of the American Livebearer Association who was breeding them in his fish room.
  • A simple setup, live foods and a sexed pair is really all it takes to successfully breed Hippocampus zosterae.

Many middle-aged and older aquarists may be familiar with dwarf seahorses, even if they don’t realize it. Those of us who grew up in the precomputer age reading comic books are likely familiar with the ads in the back of those comic books offering seahorses for sale. These were dwarf seahorses, and those of us who bought them had live fish arriving in the mail years before the Internet began.

The marine curio industry also affects wild seahorse populations. For more about this threat, go to

As a testament to their hardiness, most of those early shipments arrived alive and well. Because the dwarf seahorse is relatively easy to care for, provided a few basic needs are met, those of us who followed the simple directions that came with them were rewarded with fish that often reproduced and survived for several generations in our care. Unfortunately, I’m sure many others did not follow those directions, and those poor fish in their care did not last long.



In the Wild
The dwarf seahorse is found in eelgrass beds around coastal Florida, out in the Atlantic to Bermuda and throughout the Caribbean. In fact, their specific name zosterae refers to the genus of eelgrass with which they are most often associated: Zostera. While individual specimens are reputed to be tied to one area, and they don’t move around much, their wide dispersal is apparently due to them hanging on when pieces of seagrass break loose and float off with the current to settle down sometimes hundreds of miles away.

Keeping Dwarfs
I have kept and bred dwarf seahorses many times. They are one of my all-time favorite fish, and they are a great introduction to keeping and breeding marine fish. When I recently won a 3-gallon nano tank at a local aquarium club raffle, I decided it would be an ideal home for a small colony of dwarfs. It has worked well, and after breeding them, I have been able to share many dwarfs with my friends who want to try their hand at keeping them.

The marine hobby has certainly become much easier over the past couple of decades, and it is now easy and relatively inexpensive to get a small marine tank up and running. A setup for dwarfs is fairly simple. A fully grown adult would barely cover George Washington’s head on a quarter, with a tail about that long as well. Because they are so tiny and not extremely motile, a small tank is all that is needed. In my experience, they don’t seem to do as well in 10-gallon or larger tanks. I set up my 3-gallon nano with a quick trip to a local marine store and about an hour of work when I got home.

The tank has about a pound of live sand, a couple pounds of branchy Fiji live rock rubble and a clump of Caulerpa. It is filled with premixed “live” seawater. The small internal power filter is set on low to circulate the water. The light is on a timer and runs for 12 hours. I added a small LED moonlight that provides a bit of nighttime lighting. I did not use a heater, though it would be a good idea to add one if the room housing your tank will become colder than 65 degrees Fahrenheit. For regular tank maintenance, I change 1 gallon of water every two weeks. The used water goes into a 10-gallon refugium tank that I have set up to grow copepods, which are a supplemental food for my dwarfs.

Before I purchased the seahorses, I let everything run for a few days to make sure it was all working and then headed back to the marine store. I picked up a couple of nerite snails for algae control and a container of live copepods (Tigriopus californicus) to seed the tank, even though there were plenty of little critters already there from the live sand, live rock and Caulerpa. Because my local marine store was not able to bring in dwarfs for me, I ordered my seahorses from a reputable mail-order dealer that has been in business for many years; the seahorses arrived a few days later with the regular mail delivery.

I drip acclimated them over several hours and then introduced them to the tank. (For more information, see the “Drip Acclimation” sidebar.) They immediately set about exploring their new home, chasing down tiny invertebrates and quickly snicking them up. “Snicking” is the term for when seahorses rapidly open and close their trapdoorlike mouths, inhaling and trapping food items within. In larger species, you can actually hear a slight “snick” sound as they do this, hence the term. If I had not witnessed it before, I would have been surprised at how quickly they adapted to captivity. Now that the colony is established, I have about two dozen adult seahorses in there, along with many young, and I am able to give away half a dozen or so pairs each month. Looking into the tank, you’d be surprised to know there were that many fish in the tank!

Larger seahorse species can eat frozen foods, but dwarfs do not seem to be interested in anything that is not moving. This is the biggest caveat about keeping them. If you cannot provide them with a constant source of live food, do not buy them. With advances in modern marine aquarium husbandry, keeping them has become simple.
Set up their tank as you would a refugium, full of Caulerpa and live sand or rock, and there will always be a ready supply of food for them. I supplement this daily with newly hatched brine shrimp that is harvested within an hour or so of hatching, and I add copepods once a month. The copepods are too big for all but the largest of the dwarfs to eat, but the nauplii and juvenile pods are bite-sized. In addition, the nerite snails lay egg cases that hatch into tiny planktonic larvae called veligers. These are excellent foods for young dwarfs. This provides them with a varied diet and plenty of hunting opportunities.

In the past, I have fed my dwarf colonies exclusively on newly hatched brine shrimp and have had multi-generational success with just this single food. Some marine breeders say that this is not nutritionally adequate and that one cannot successfully raise dwarfs on this single food, but I have had multiple generations do just fine. I think the difference is that I feed brine shrimp nauplii as soon as they hatch to my dwarfs, while some breeders feed the nauplii when they get around to it — sometimes up to a day or more after they hatch — when most of their nutritional value has been turned into energy and used up.

One interesting thing I’ve observed with multiple colonies at different times over the years: Dwarfs seem to learn the flow of the current in their tank. When they see you coming with food, they all begin to gather in one area where the current tends to bring the food. Each one has its own hitching spot, and they sit there waiting for the food to come to them. For such tiny creatures, this obvious learning behavior is amazing to witness.

Drip Acclimation
To safely acclimate your seahorses and many other types of fish to your tank, use the following drip acclimation method.  

  1. Pour the fish and their shipping water into a fish-safe bucket or similar container. I use plastic containers made for reptiles and small animals with a snap-on top. They have a ready-made hole for an airline tube.
  2. Set up a drip line by using a piece of airline tubing and draping it from the tank down to the container with the fish.
  3. Start a siphon and allow the water to drip into the container. Regulate the flow by kinking the tube and wrapping a rubber band around the kink until about one drip comes out per second. I use a small air valve that allows me to easily increase or decrease the flow. Allow this to run until the water in the container is about double what it was when you started.
  4. Carefully pour off most of the water until there is just enough to cover the fish when they are upright. Let the container fill again. This procedure slowly introduces the fish to your water and allows the temperature to equalize. It’s not a bad idea to add an ammonia neutralizer to the water, too. This will help reduce stress on the fish while they are adapting to your water.
  5. Once the container fills again, the fish will be in about 90 to 95 percent your water. Carefully net the fish out and move them to their new home. Do not add the shipping water to your tank.

Dwarf seahorses are precocious and will breed freely in captivity. Some seahorse species are reported to be monogamous, but dwarfs definitely like to play the field. I have one large female that mates on a regular basis with at least four different males. Their mating dance usually happens early in the morning, and I’ve never seen a pair mate in the afternoon or evening.
The pair circles each other while attached to a piece of Caulerpa, often with their tails touching. The male pumps his pouch, often inflating it nearly as full as a male about to give birth. Both fish intensify in color and do a little shimmy dance side to side and up and down. They sometimes change color or go from a solid color to a mottled color almost in the blink of an eye. At the end of the dance, the male and female touch vents and sometimes rise in the water column 1 or 2 inches off of the Caulerpa. In a few seconds, it is over, and both fish go their own way with the male usually settling back down to his hitching post while the female moves off.

Giving Birth
A dwarf’s gestation period is about 10 days at 70 degrees Fahrenheit. The male carries up to a dozen or so eggs in his pouch, and each day it swells a bit as the embryos grow inside him. Recent studies have shown that a pseudo-placental structure develops, and the lining of the pouch changes during embryonic development.
After 10 days, the male will be bulging and obviously in distress. His color darkens, and he begins what appear to be contractions, twisting and contorting his body while sometimes rubbing the pouch against solid objects. The baby seahorses (usually called “ponies”) are expelled one at a time. They just pop out and shoot an inch or so away. The ponies immediately swim to some solid surface and grab on. The adults ignore them. The newborn seahorses are barely a quarter-inch long, but they are exact copies of their parents and can easily handle surprisingly large food items. Within five to 10 minutes after birth, they are actively hunting for food. Interestingly, young ponies almost always hang upside-down while hunting for the first few days.

Are you also interested in regular-sized seahorses? Find out all about how to care for them at

The young ponies need a lot of food and grow quickly, doubling in size in just a week. Some texts report that they can consume 1,000 brine shrimp nauplii per day. Other writers have witnessed the young ponies snicking so much so quickly at feeding time that they are literally passing live brine shrimp nauplii out one end while snicking it in the other. I thought this was ridiculous until I witnessed it myself on several occasions. Since seahorses have rudimentary stomachs, I guess they are not capable of holding much food, so excess food just goes right on through.
Dwarf seahorses are amazing animals. I see something new and different each time I look into their tank. I set up the tank right in my office next to my computer, so I can watch them all the time. Of course, sometimes that distracts me when I’m writing! The only drawback is that they need to have small, nutritious live foods all the time. If you can meet this one non-negotiable requirement, give them a try. A colony of dwarf seahorses makes an excellent display in a 2- to 5-gallon nano tank and might even get you interested in trying your hand at keeping and breeding other marine fish.  FAMA



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Fish · Saltwater Fish