Hippocampus reidi fry are best raised in kriesel nurseries at reduced salinity and the proper degree of turbidity to keep the pelagic fry away from the surface. The fry are very challenging to raise because they are too small to eat newly-hatched Artemia as their first food and undergo a lengthy free-swimming or pelagic phase that lasts several weeks.
For best results, the fry need to be started on live rotifers for the first week or two before you wean them on to first-instar baby brine shrimp. The rotifers in turn must be fed on microalgae or phytoplankton, also known as greenwater. So in order to raise reidi fry, you must first culture rotifers and phytoplankton. These cultures can be continued indefinitely, but they are prone to crashing for various reasons.
If you look up the previous thread on this discussion board titled "reidi fry — no survivors," my responses in that discussion should answer most of your other questions raising reidi babies, Nigel. You can look up the discussion at the following URL, and it will direct you to an article that explains one good way to culture rotifers and the greenwater/microalgae they feed upon:
Click here: Seahorse.com – Seahorse, Sea Life, Marine Life, Aquafarm Sales, Feeds and Accessories – Re:reidi fry no survivors
You could transform your five-gallon nursery into a kriesel by using a bubble wand or bubble curtain to establish the circular flow, Nigel.. Sometimes the most effective pseudokreisel nurseries are also the simplest. One such design uses a bubble wand or air bar positioned tightly against one side of the aquarium to disrupt the surface tension and create a slow, circular current. If the tank is rectangular in shape, the bubble wand should be secured at the bottom of one of the long sides of the aquarium.
Aside from its simplicity, the beauty of this system is its versatility. It can be scaled up to whatever size nursery is required or desired. For example, Jorge A. Gomezjurado used this exact type of pseudokreisel for a 90-gallon nursery at the Steinhart Aquarium, where it proved to be very effective for raising huge broods of pelagic Hippocampus ingens fry. Jorge notes the circular current (the kreisel effect) works well for keeping the fry away from to top and keeps the developing young and their food dispersed uniformly through the nursery tank (Gomezjurado, pers. com.).
A variation on this type of nursery adds drip bars or spray bars positioned just above the water level to create additional surface turbulence. When used in conjunction with the back-mounted bubble wand, the spray bars enhance the effectiveness of the circular flow pattern in nudging the fry away from the surface. This combination of surface agitation plus the kreisel effect is very efficient at preventing pelagic fry from getting stuck to the sides and entrapped by surface tension (Bethany Watson, pers. com.).
As you know, it’s never a good idea to transfer a pregnant male into a paternity tank with strange, new surroundings. If you must do it because the filtration in your reef tank will "eat" the newborn fry, proceed very carefully, make the nursery tank as stress free as possible for the gravid male, and make sure you stay on top of the water quality to prevent any ammonia spikes! It’s a much better idea to time his pregnancy so you can be present when he gives birth and gather up the fry from the main tank before they’re at risk from the filters. Gestation in H. reidi is typically about 14 days at 78°F-80°F.
In short, Nigel, I suggest you install a bubble wand or bubble curtain and perhaps add a spray bar to your 5 gallon nursery as described above, and then reduce the specific gravity in your nursery tank to around 1.016 in order to reduce your problems with surface huggers and floaters. Make sure you don’t expose the newborn fry to the air when you transfer them and you will start off on the right foot.
H. reidi fry grow relatively slowly, so I wouldn’t consider transferring any juveniles who managed to raise into the main tank with their parents until they are around six- month old and have put on some size. Transfer the juveniles from the nursery tank into a larger grow-out tank after you have wean them onto frozen foods.
Best of luck with your pair of H. reidi, sir! Here’s hoping they produce many healthy broods for you in the months to come!