A Rough Ride with a Tiny Horse
Hippocampus zosterae, the Dwarf Seahorse

by Mike Hellweg
First published in The Darter, Missouri Aquarium Society
Aquarticles

The Dwarf Seahorse, Hippocampus zosterae, is a truly diminutive creature. The name in print on this page is longer than the fish is in real life! It is a truly amazing animal that many people don't even believe exists. Until recently, it was the smallest member of its genus. But now two more diminutive Seahorse species have been found - one of them just within the last few months. A fish that swims upright with the head of a horse; a high-powered vacuum/trapdoor contraption for a mouth; an armor plated body shaped like the knight of a chess set; a prehensile tail like a monkey; a nearly invisible dorsal fin that beats 75 times a second; males that go through labor and give birth to living young; eyes that move independently of each other like those of a chameleon; the ability to change color; and even to grow camouflage. Wow! And it's for real, not a creature of fantasy!

Ever since I was young, I've seen the ads in the classified sections of various magazines: "Live Sea Horses! Males give birth to cute Sea Ponies! For just $1.00 (okay, I've seen the ads for a LONG time!), you can bring these mystical creatures into your home!" I love reading ads - ads of all kinds, but especially aquarium and hobby related ads. It often amazes me what the adman will come up with to get you to buy whatever it is that he is hawking. Remember Sea Monkeys™? What an amazing ad campaign for brine shrimp! But the amazing thing about the ad for the Seahorse is that it doesn't have to make anything up to make these fascinating creatures desirable. The only drawback, and it is a big one, is that they are difficult to properly care for. In fact, aside from the Dwarf Seahorse, most Seahorse species are better left to the dedicated specialist, or in the wild. In this article I want to share some of my experiences with trying to keep and breed these magnificent miniatures.

Earlier this year, a hobbyist looking for some of the fish I had for sale on Aquabid contacted me. He wanted to trade, not buy fish. Usually I'm not too interested in doing this since you don't really know with whom you are trading and there is no umbrella organization like the AKA or ACA to regulate the trade. But what he offered in trade was too tempting! He had a group of tank raised Dwarf Seahorses that he wanted to trade for a group of my Swordtails! I hastily accepted. I could afford to loose a group of juvenile Swords and the postage for the chance at getting a group of the long-coveted Dwarf Seahorses - and tank raised at that!

I quickly set up one of my Show tanks (which I normally keep just for the MASI annual show) for the Seahorses. It's one of those fancy Marineland Eclipse 6-gallon tanks with the wet-dry power filter and light fixture built in. It would be perfect! I filled it with 6 pounds of crushed coral and mixed the salt mix into a 5-gallon bucket of water. I did not add a heater - they would be fine at room temperature. Kathy Deutsch helped me out with a starter of Caulerpa, (a funky wiry species I have not identified yet) and I picked up 5 pounds of live rock. The tank was ready. While I was waiting for the Seahorses to arrive, I started seeing all kinds of little critters crawling about the tank. This came back to bite me, but more on that later.

I shipped out the Swordtails right before one of the interminable snowstorms we experienced last winter moved in. They arrived just fine, but we decided to wait until later for him to ship the fish to me. About a week later, he shipped the fish. And another one of those nasty snowstorms rolled in. My mail carrier carefully delivered the tiny box to me 3 days later. I was amazed. He didn't use my comparatively giant box (12 x 12 x 12 styro) to ship the fish back. He put them into a 5 x 5 x 5 cardboard box! There was no styro - they were wrapped in newspaper! I figured they would be dead for sure. I carefully unwrapped the bag, expecting the worst. But they were all fine! The water temperature was 56°F, but they were all swimming around the bag looking none the worse for wear. Here I learned Lesson #1 - they are VERY hardy!

I put them into a small bucket, and started a drip line from the tank to the bucket. I did not want to warm them up too quickly, so I tied a knot in the line to slow the drip to just a drip every five seconds or so. A couple hours later, they were swimming in a bucket of mostly my water. I carefully netted them out of their bucket and put them into their new home. I refilled the difference in tank water with some more fresh salt water that I had mixed up the day before - never add the shipping water to your tank. Here I learned Lesson #2 - they are deceptively fast and are more difficult to net than you would expect! They can really get moving when they need to! They straighten out and go for broke. And they can hang onto the edges of the net and refuse to let go! Moving them to their new home was an amusing and interesting experience.

Once in the tank, I could see them more clearly. I had 9 fish - 7 females and 2 males. And one of the males was bulging. They settled in quickly, and went about exploring the tank. Here I learned Lesson #3; a six-gallon tank is too big for 9 Dwarf Seahorses. As they settled in, they disappeared! It took me a little longer each day to find them as they got better and better at blending in with their surroundings. People who visited the fishroom just smiled and said something like "sure, there are all kinds of Seahorses in there!". If I couldn't see them and I knew where to look, I guess they could not see them at all!

As soon as they were all in their new home, I gave them a feed of newly hatched brine shrimp. Here I learned Lesson #4; the Eclipse Six filter is very efficient! It removed most of the live baby brine within a few hours. After this, I turned off the filter whenever I fed the fish. But the Dwarfs also learned; they started hanging around the inlet to the power filter when I turned the filter back on. Smart little guys!

NEWLY HATCHED brine shrimp is the preferred food for Dwarf Seahorses. If it is more than 36 hours old, it needs to be fortified with a HUFA (Highly Unsaturated Fatty Acid) supplement like Selco®. If it is NEWLY hatched, it still has plenty of nutrient value for the Seahorses, and can serve as their sole diet, unlike with the larger Seahorses. After the third molt, which occurs at about 36 hours post hatch, the brine shrimp has little nutrient value and needs to be fed (or "loaded") with a supplement to make it more nutritious.

The next day after arrival, the bulging male presented me with 3 baby seahorses. Two of these were stillborn (I assume from the stress of shipping), but the third was actively exploring the tank looking for food. It was a long, skinny, miniature copy of mom & dad. All stretched out, it would have been barely 3/8" from tip to tip. I figured the live baby brine would be too large for it, but it managed just fine. I watched for a while, and it carefully stalked and ate several shrimps while I watched. Hey, this was going to be easy! Yeah, right…

A little less than two weeks later, the same male presented me with a batch of 8 little ponies. The other male never did produce any fry - maybe he was already beyond his reproductive age - I don't know. I didn't realize how much the first pony had grown until I saw the newborns. Wow! They grow fast! I put a nylon net breeder in the tank to allow the fry something to hang onto so they could feed near the surface where the majority of the brine shrimp congregated after an hour or so. Here I learned Lesson #5 - They are eating machines! Within a few hours, most of the brine shrimp was gone, and the babies were bulging - so were the adults.

I did some research in a couple of books on Seahorses and found out that the gestation period of the Dwarf Seahorse is only 10 days! Not only do they grow fast, but they develop quickly from egg to pony! During their breeding season, the male is almost always in some stage of pregnancy. It didn't take long until that one little male had produced quite a few little ponies. I have also read that male and female seahorses pair bond. Some authors claim it is for life, others claim it is just for one breeding cycle. Well, that little stallion and those little fillies certainly never read those accounts. At one time or another, I saw him entwining tails with at least 4 of the 7 females! Interestingly, the other male never seemed to be interested in the girls, only in food. He was always the first one to the feeding area when I was in the fishroom.

As I became more familiar with my fish's behavior, I was able to watch the mating dance of the seahorse. It is much more elaborate than that of the other livebearers I have observed. The male puffed his pouch at the female; they bowed to each other, entwined tails, and rose up together in the water column with their bellies touching. They did this several times, and I guess one of these times the female actually transferred eggs to the male. Some sources mention that you can sometimes see the eggs, as one or two miss the pouch and fall to the bottom of the tank, but I did not see this.

Here are some other tidbits that I learned through reading and observation - they are presented in no certain order: Dwarf Seahorses spend much of their time hanging upside down in the current, searching for food. Don't get excited, this is normal. They seem to change color fairly regularly due to changes in mood, etc. Each fish looks a bit different and you can easily recognize individual fish after a while. Certain fish seem to have a certain "basic color" that they maintain most of the time, but it darkens and lightens throughout the day, and as they interact with one another. Dwarf Seahorses have small broods - even large males will only deliver 8 - 10 ponies. Males seem to be always pregnant during mating season. They usually mate within a day or two of delivery. Don't let them go even a day without food - they don't have a proper stomach, and due to their exoskeleton they do not build up fat reserves, so they need to eat constantly. If you can't provide food for them on a daily basis, don't try to keep them. Young Dwarf Seahorses will also eat freeze-dried Cyclopeeze. I tried the frozen stuff, too, but they seemed more interested in the way the freeze-dried stuff floated and twisted in the current. You can have quite a few Dwarf Seahorses in a 6-gallon tank. At one point I had more than 40 of them happily swimming about. But that is where disaster set in.

At first, I lost a few of the adults. The other male that didn't deliver any fry went first - I suspect due to old age. Dwarf Seahorses only live for about a year, and he may have already been 10 months or more old when he arrived. Then I noticed that there were fewer fry coming up to feed. At about the same time, I noticed a large bloom of Hydroids, including a group that sexually reproduced and produced their free-swimming, jellyfish like Medusa stage. Hydroids eat live baby brine just like the Seahorses, so they were prospering on the same food as my fish. For those of you who don't know what they are, Hydroids are a group of animals related to Anemones, Hydra, Corals, Jellyfish, and other stinging animals. They look like miniature Anemones, with a fat oral disk and short, fat tentacles. They don't eat adult Dwarfs, nor do they seem to eat baby Dwarfs. But they do sting them and can cause fatal injuries to the ponies. Everything I read said that there was no cure, that I was doomed to failure.

But there is a cure - the same thing many hobbyists use to kill Hydra in freshwater tanks. I dropped a quarter tablet of Fluke Tabs® into the filter. The next day, all of the Medusae were gone, and most of the Hydroids had closed up. By the end of the week, all of the Hydroids were gone, and I haven't seen any since. However, the Fluke Tabs® kill other Inverts, too. I lost a nice group of Feather Duster Worms that was growing on the live rock, some sponges also declined and later died, and I lost several other little creepy crawlies that were pretty neat. Since then I haven't seen the tiny little starfish that came with the live rock, either.

But even after this, day by day I was seeing fewer Seahorses, and no bodies. Something was going on - but what? I pulled all of the live rock out, looked it over closely, and put it back in - nothing there. Or so I thought! Here I learned lesson #6 - the nasty little creepy crawlies can hide VERY well. A few days later I found my very pregnant male sticking out of a little hole that I had not noticed before. I gently pulled on him, he struggled a bit, and something pulled back! Eventually I worked him out of the hole, but not before the tiny Pistol Shrimp that held the other end had done fatal damage. The Pistol Shrimp disappeared back into his little hole. I removed the live rock immediately from the tank. Mr. Pistol Shrimp wasn't going to get anymore fresh Seahorse meals! This is where I learned Lesson #7 - don't use live rock with Dwarf Seahorses. Too many of the cute little creepy crawlies that come with it can be deadly to your little Seahorses. Live rock is great in other situations, but keep it out of Dwarf Seahorse tanks! Since I removed the live rock, I haven't lost a single Seahorse. Unfortunately, all of the fish I have left are females. So I guess I'll have to break down and respond to one of those ads in the back of the magazines to get another male! After all of these years - the adman will finally get me!

To summarize the basic care requirements:
1. Small marine tank - the smaller the better. A 2-1/2 gallon tank would be perfect.
2. Standard marine mix - around a specific gravity of 1.024. Room temperature is fine - but keep it below 80°F.
3. A sponge filter is fine; in fact, it's probably better than the power filter I use.
4. Give them plenty of attaching places. Plastic plants, Caulerpa (first treated with Fluke Tabs®), and other décor work great.
5. Add a few tiny inverts to help with cleanup - turbo snails for algae control, maybe a small starfish, and a few tiny shrimp (the little ˝" red guys from Hawaii are best - though I don't know what they are called).
6. Feed NEWLY HATCHED live baby brine shrimp daily - and feed a lot of it. They eat more than you might think! One of the studies I read said that a young seahorse could eat 3000 baby brine shrimp every day.
7. Don't use Live Rock or untreated (with Fluke Tabs®) Caulerpa. Don't add any predatory shrimp or large starfish (which can also eat small seahorses!). Also, stay away from Hermit Crabs - even the tiny ones will eat the Dwarfs if they get a chance. Also, if you want to try keeping marine fish - use another tank. The Dwarfs just won't be able to compete with them for food.
8. Watch them and enjoy their unique behavior!