Raising Seahorse Fry: The Fish Bowl Method
The system I use for raising Hippocampus reidi fry is a modified pseudokreisel. Kreisels and pseudokreisels are tanks with a circular water flow most often used for keeping jellyfish. For H. reidi, and other pelagic seahorse fry prone to air snicking, you can use a drum fish bowl for this purpose.
The design originally suggested by Pete Giwojna was an airline tube, glued half way down the curved side. This makes the water flow in a circular pattern that pushes the fry away from the top and prevents them from gulping air.
About the same time I learned about this, I discovered by accident that a batch of fry did better in a “dirty” tank, a tank I didn’t clean out from before the last brood that had failed. I’m now sure it was due to the large number of copepods that had grown from eating the bodies of dead seahorses. Martin Moe even made note that his orchid dottybacks did better in “dirty” tanks in his breeding orchid dottybacks book. If that wasn’t encouragement enough…
So I set out to merge the two systems, and now I use a 4 gallon plastic drum fishbowl with a sponge filter glued to the side. I make my own sponge filters out of open celled furniture foam, which is available at most fabric stores. Opened celled foam means the cells that make up the foam are interconnected and can pass air, water, etc . . . Since it’s not very likely the store will know if it is or not, you’ll have to test it – which means blowing into it and seeing if you can feel your breath on the other side.
Once you have the foam, you’ll need to cut and drill it. I soak it in water and then freeze it, which allows you to saw and drill it more easily. This is especially important for drilling, when the foam very easily binds up the drill.
The shape I make is roughly a square with an angled bottom. (see picture in below link). I usually make it taller rather than longer/wider. Then drill a 1/2 inch hole in the top about half way to three quarters the way down for the uplift tube. From the side that will be facing the inside of the bowl, I drill a whole just wide enough to fit rigid airline tubing – it should meet the uplift tube hole at the very bottom of that hole.
When the foam is drying, I work on the uplift tube. This requires caution because I use a small blow torch to melt the plastic. In other worlds, follow these instructions at your own risk, and make sure to do it in a well ventilated area, as most plastic fumes are hazardous. I cut the length so it goes about a half inch to an inch into the uplift tube hole in the foam, and the rest can be bent so it is just shy of the side of the fishbowl. I heat it up, and bend it with whatever tools I have handing – pliers, fork, pencil… then rinse it under cold water to set it.
Once that is done, cut the rigid tubing so it has an inch sticking out of the foam, and goes back to the beginning of where the rigid airline hole meeds the uplift hole. I glue it in place with silicone glue. I then cover the back side of the sponge filter in glue, and place it along the curved side of the wall near the bottom so that the bent uplift tube meets the fish bowl side about half way up. Then it dries for 24 – 48 hours.
To get the bowl ready for fry, I like to start a month in advance, but two weeks is usually enough time to get by. Unless the aquarium has a known population of hydroids, I start with water from the parents tank. If I have a separate culture, I add copepods and rotifers. If not, the copepods SHOULD be present in the parents tank water, although it helps to siphon the glass of the tank at night.
Once its set up, I add small amounts of food until I see copepods swarming around it, and then start adding more. Frozen mysis and frozen squid seem to work especially well for this, although flake food will work too. If you’re going to add rotifers, now is the time, along with microalgae. Once most of the food is eaten by the copepods, add more food.
When the baby seahorses arrive, change at least half the water with water from the parents’ tank. I transport the babies in the parents’ water after catching them underwater by either using a brine shrimp net and transferring from net to plastic bag underwater, or siphoning them up with an airline hose. This may provide you with enough water. You’ll need to judge the amount of current based on fry behavior. I usually end up turning up the airflow pretty high to keep them off the surface. The appropriate amount of air may seem like a lot, but keep in mind in nature, they’re disperse via the choppy waters of the ocean, so they’re designed to handle it. The fry wishing to “rest” will make their way to the center of the bowl where the current is much less turbulent and hang there.
The seahorse fry will still need to be fed baby brine shrimp, and if they eat the copepods and rotifers too quickly, supplemented with both. But it does get them a great head start on eating. Some won’t take bbs at birth, but will happily take copepods off the sides or when they swim in the water column.
With this system, I do water changes just once a week. It is a real life saver to not have to do water changes every day the first week when they’re so tiny and hard to work around.
I’m still experimenting with what age to move them from this system. At about a month, most have hitched and are preferring to hitch over swimming. However, they still can and do snick air at that age, but not nearly as easily when they are in their pelagic stage. At about six weeks old a power filter (intake well protected) is usual enough to keep them off the surface.
Also about that age, they need to start the switch to larger intermediate foods, the in between foods before they learn to eat frozen. You’ll need to continue to feed bbs and copepods, as they make the switch gradually. The foods can include quarter sized brine shrimp (enriched, of course), juvenile mysis shrimp, baby amphipods, or any other crustaceans that small (peppermint shrimp fry make a great food item at this stage). Without the intermediate food, most will just lose interest in bbs and die. Those that continue to eat bbs may become stunted, especially if they’re not quick to switch to frozen.