Re:Baby Mustang trouble

Pete Giwojna

Dear David & Sheena:

Congratulations on the new juveniles. As long as both of the youngsters are eating well, breathing normally, and can swim without any difficulty, then I would not be overly concerned if one of them tends to spend more time on the bottom of the enclosure, while the other one is a more active swimmer. As long as the bottom hugger can ascend and descend without any difficulty when it is swimming, then you can be sure it is not a problem with an underdeveloped or underinflated swimbladder.

In my experience, when juvenile Hippocampus erectus begin to spend more time on the bottom of their nursery, that’s often an indication that they are ready for more substantial food than newly hatched brine shrimp. So my best guess is that the youngster that spends more time on the bottom of the tank is ready to begin feeding benthically rather than feeding on brine shrimp nauplii suspended in the water column.

In other words, David and Sheena, I think it’s time that you begin weaning your juvenile Hippocampus erectus onto frozen Mysis and other more substantial food, as we will discuss later in this message. But first, I wanted to mention a couple of things you need to keep in mind when using an in-tank nursery, such as the breeder net.

For instance, one thing you need to be aware of is to monitor the ammonia and nitrite levels closely now that you are keeping the juvenile seahorses in the breeder net within your main seahorse tank. The copious amounts of newly hatched brine shrimp the juvenile seahorses require, and their equally rapid fecal pellet production, will be contributing greatly to the bioload in the level of organic wastes in the aquarium, and you’ll need to make sure that the biological filtration ability of your seahorse tank can handle the heavier bioload without any spikes in the ammonia or nitrite levels.

Another thing to remember is that you must keep the breeder net scrupulously clean for the sake of the juvenile Hippocampus erectus, David and Sheena, because it will tend to become dirty and unsanitary relatively quickly.

The first in-tank nurseries were ready-made breeder nets intended for live-bearing freshwater tropicals (Abbott, 2003), just as you are using for your juvenile erectus, David and Sheena I. I know several hobbyists who use breeder nets for rearing dwarf seahorse fry. They tend to get a bit dirtier than bare-bottomed nurseries (uneaten brine shrimp and fecal pellets will accumulate on the netting and cling to the mesh) so you’ll need to be diligent about siphoning the netting clean of such wastes and debris, just as you would be when cleaning the glass of a bare-bottome nursery. The dirty water should be replaced with cleaned, newly mixed saltwater you’ve prepared and aged/aerated overnight. These small water changes will help maintain good water quality in the main tank.

Many hobbyists who used these breeder nets for rearing fry keep two of the nets, one which is in use as a nursery, and a clean spare which they transfer the fry into when the breeder net that’s currently in use gets too dirty and unsanitary despite the siphoning. The dirty net is then cleaned and disinfected thoroughly and held in reserve until the other breeder net needs to be replaced. The two breeder nets are then switched back and forth as often as necessary to assure that fry are always contained within a reasonably clean enclosure.

Finally, David and Sheena, if the new juveniles are 1-1-/2 inches in length, they need a more substantial diet than newly hatched brine shrimp, and they are ready to be weaned onto frozen foods. They should be receiving brine shrimp at advanced instars, including adult brine shrimp, at this size, and you should begin weaning them onto minced frozen Mysis and other frozen foods at this point, as discussed below.

Making the Transition to Frozen Foods

The current thinking is that the fry can remain on a steady diet of newly hatched Artemia until you are ready to begin weaning them onto a diet of frozen foods (usually minced Mysids and/or Cyclop-eeze). Aquaculturists are now converting the fry to frozen foods earlier than ever, often beginning around 3-4 weeks old. Jeff Mitchell reports that the fry are healthier and grow faster the sooner they make the transition to enriched frozen foods, and he expects the young seahorses to have made the transition to frozen foods by the age of 4-1/2 weeks.

I generally have the best results using frozen Mysis. The best way to prepare the Mysis for the juvenile seahorses is to mince the frozen Mysis coarsely rather than putting it through a blender. How fine or coarse you need to chop it depends on the size of your fry, since you want to wind up with bite-size pieces of Mysis. Initially, many breeders prefer to shave small pieces of Mysis off of a cube while it’s still frozen.

The frozen Mysis that works best for most hobbyists is Hikari in frozen blocks rather than trays. The Hikari Mysis is much smaller than Piscine Energetics Mysis relicta and that makes it easier to shave off bite-sized pieces for the young seahorses. Some hobbyists report even better results using the new Mini Mysis offered by H2O Life, which is small enough that it often doesn’t need to be minced or shaved before offering it to the juveniles.

When it comes to shaving the Mysis, a technique that works well for many home hobbyists is to use a potato peeler to shave off bits of the Hikari Mysis from a frozen block, and then use a single edged razor blade to further mince the frozen bits the potato peeler has removed.

Try offering the minced Mysis exclusively for their first feeding of the day when the youngsters are the hungriest. Watch the juveniles closely to see if any of them begin to pick at the minced Mysis or pick it up from the bottom. If they still aren’t having any of it, siphon up the uneaten frozen Mysis after about half an hour and offer them newly hatched brine shrimp soaked in Mysis juice so that they have something to eat, and intermingle some freshly minced Hikari frozen Mysis or Cyclop-eeze in with the bbs.

When the fry have grown a little larger and can accommodate bigger pieces of Mysis, I find it convenient to carefully thaw whole Mysis individually and then carefully chop them into several pieces. Or the Mini Mysis by H2O Life can be fed to the larger juveniles whole and intact, if you can obtain it.

Either way, it is very important to be extra diligent about vacuuming up leftovers (and any fecal pellets) while the fry are making the transition to frozen Mysis. Otherwise, the minced Mysis that doesn’t get eaten right away while it’s still suspended in the water column or shortly after it has settled on the bottom will begin to degrade the water quality in your nursery tank.

It’s important to overlap the fry food when they are making the transition. Offer them shaved or minced Mysis along with the newly hatched brine shrimp they are accustomed to eating. (Many times it’s better to offer the minced Mysis first, while the fry is still the hungriest, and then add the baby brine shrimp.) Once they begin eating the bits of frozen Mysis well, gradually increase the amount of minced Mysis and decreased the amount of baby brine shrimp you offer at every feeding until they are finally eating the shaved Mysis almost entirely.

Overlapping the feedings this way, offering newly-hatched brine shrimp as usual along with just a little frozen Mysis at first, assures that there is familiar food available to the fry while they are making the transition and makes sure that the slow learners still get enough to eat.

Some hobbyists find it helpful to begin soaking the newly hatched brine shrimp in Mysis juice for a week or two before they actually began offering the bits of minced Mysis along with the bbs. That way, the juveniles get used to the scent of the frozen Mysis and associate it with food before you start to add the bits of frozen Mysis.

Here’s a previous message from Patti that describes how she weaned her erectus fry onto frozen to Hikari Mysis:

[open quote]
I’m wondering if nutrition is your problem.
Could you train them onto frozen mysis? My 4 week old erectus are eating shaved Hikari frozen mysis already. They started not eating much of the BBS and looking around the bottom of the bowl. I enriched the shaved mysis w/Vibrance & put it in the bowl. It goes to the bottom and they’re on the hunt. They’ll look at it a good while and then snick. It only took 1 day to train them. I swish it around a little at first to get them interested.

I think the mysis is better for them nutritionally and they don’t have to spend so much energy eating all those tiny BBS. Give it a try. It may take a few days. I gave mine the mysis 1st – before adding the BBS. That way they were pretty hungry. Then I gave them some BBS for desert to make sure each one got something to eat if they weren’t eating enough mysis yet.
Patti [close quote]

Notice that Patti’s erectus fry were all hitching and beginning to look around on the bottom for things to eat, indicating that they were ready to give up their planktonic existence (i.e., the high-risk pelagic phase) and make the transition from live brine shrimp suspended in the water column to frozen foods.

Other breeders go a step further and begin adding a little of the minced Mysis to their nursery tanks with the newborns right from the start to help build up their intestinal flora and ultimately enable them to better digest the frozen Mysis when they start eating it. They feel that this helps the babies get them used to the scent of the Mysis and conditions them to associate it with food, which helps to make the transition from live food to frozen Mysis easier later on when they’re the right age.

For example, here’s how Neil Garrick-Maidment, a very successful breeder in the UK, describes this technique:

Hi Peter and all,

I tend to put in a very small amount of finely chopped mysis in with the fry from day 1. The idea behind this is to create a bacterial soup in the fry water to help load the fry gut with the right bacteria to break up the mysis shrimp which tends to be quite hard. It makes it easier to get them to switch to dead mysis later on BUT it is crucial to clean the tank daily and water change to stop a problem with disease..

Neil Garrick-Maidment

Cyclop-eeze is also worth considering when weaning the youngsters onto frozen fare. When the juveniles are the right age, don’t hesitate to try them on frozen Cyclop-eeze first if you aren’t having any luck with the frozen Mysis. Lelia Taylor is one hobbyist who has had good results using the Cyclop-eeze, as she described below:

<open quote>
I have had success placing BBS in Cyclop-eeze, then feeding the mixture to my babies. They readily take the Cyclop-eeze. As they get bigger I add frozen, enriched brine shrimp. they began eating the frozen food immediately. Using the same principle, I began adding Mysid shrimp, along with the brine shrimp and Cyclop-eeze. I have found, even very young babies, will pick the larger pieces of Mysid shrimp, into bite sized pieces. I have also had success culturing copepods in my baby and grow up tanks. The babies readily feed on these, as well. <close quote>

Hobbyists who have tried The Cyclop-eeze for their juveniles are unanimous in saying that the frozen Cyclop-eeze is far superior than the freeze dried product for this purpose. They report that the bars of frozen Cyclop-eeze in particular work well because they will shed copious amounts of the bite-size frozen cyclops into the water.

Bonus tip: adding one or two older juveniles that are already eating the frozen Mysis well to the nursery tank along with the inexperienced fry in order to act as their mentors can hasten the transition. Many hobbyists report that fry learn to take frozen minced mysids much faster and easier when they are provided with teachers to show them the way. These teachers are usually a few of the older fry from a previous brood, which have already become proficient at feeding on the frozen mysids (Liisa Coit, pers. com.). The younger fry are quick to copy them, learning from their example.

Okay, David and Sheena, that’s the quick rundown on rearing seahorses and eventually weaning them onto a diet of frozen Mysis. It can be tricky weaning the juveniles onto a staple diet of frozen Mysis, and you need to be prepared to make water changes and to be very diligent in cleaning up the breeder net and uneaten shaved Mysis while the youngsters are getting the hang of it. But once they are weaned onto frozen Mysis, the juveniles will grow rapidly and will be ready to introduced to the main tank within 2-3 months or less.

Best of luck with your new arrivals, guys!

Pete Giwojna

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