You’re very welcome, sir!
Yes, if you will be keeping Pixies for dwarf seahorses (Hippocampus zosterae) you’ll need to maintain a couple of brine shrimp hatcheries in order to provide them with copious amounts of newly-hatched brine shrimp on a daily basis. However, it’s not necessary to put the hatcheries into operation until a day or two before the seahorses are due to arrive. That will provide ample time for the first hatch of baby brine shrimp to emerge so you can feed the new arrivals.
If you want to practice your brine shrimp hatching technique ahead of time to make sure you’ve mastered the process, that’s fine, but there’s no need to add the newly hatched brine shrimp to your aquarium until the seahorses are there to eat it. The snails and micro-hermit crabs that comprise your cleanup crew are scavengers and don’t eat the live brine shrimp.
There really aren’t any hard and fast rules regarding the proper feeding density for Pixies or dwarf seahorses (Hippocampus zosterae). However, when you’re feeding them, bear in mind that these miniature marvels are strictly ambush predators that wait for their prey to come to them and blunder within striking distance, rather than chasing after live prey at all.
Because they are so sedentary and because there are almost always newborns and juveniles present when you are maintaining a colony of dwarf seahorses, I tend to feed my Pixie tanks much like I would feed a nursery tank. In other words, I provide them with many small feedings throughout the day, and try to add enough brine shrimp so that the water has a "snowy" appearance at first but not too much, so that most of the Artemia nauplii have been eaten within about a half an hour. If I had to try to quantify this, I would say that you should try to maintain a density of approximately15 nauplii/ml when newborns or juveniles are present.
Otherwise, if there are no fry in with the adults, or if you prefer to raise the newborn Pixies in a separate nursery tank from the adults, a couple of large feedings daily will usually suffice for the main tank. Pixies or dwarf seahorses do not need to be fed any particular time of day, but it’s best to provide them with copious amounts of newly-hatched brine shrimp (Artemia nauplii) at least twice a day. A feeding schedule that works well for most folks who keep Pixies is to give them a heavy feeding of baby brine shrimp before they leave for work or school in the morning, and then another heavy feeding when they return from work or school in the afternoon.
Newborn dwarf seahorses eat the same food as the adults and can be raised right alongside their parents in the same aquarium if need be, but for best results, you need to alter your feeding regimen and maintenance schedule somewhat when you are raising the fry. For example, the adults do well with two feedings a day, but the babies require more frequent feeding and will do better if they are fed 3-5 times a day. Ideally, newly-hatched brawling shrimp should be available to the young at all times so they can feed at their leisure throughout the day. And when you are feeding more often, you will also need to perform more frequent water changes and siphon fecal pellets up regularly in order to maintain water quality, as discussed below.
Cannibalism is unknown in H. zosterae, and one of the neat things about them is that the fry can be reared in the main tank right alongside their parents since the newborns eat the same foods as the adults. However, to maximize growth and improve survivorship, the fry should be reared in a separate nursery tank where the hobbyist can maintain better control over their feeding, growth and development (Bull and Mitchell, 2002, p57). A basic benthic nursery with sponge filters works great for this and can be set up in much the same way as the adult tanks.
More frequent maintenance is required for the nurseries, however. With heavy, continuous feedings in such a small volume of water, regular siphoning is necessary to maintain water quality (Bull and Mitchell, 2002, p57). Fecal pellets and debris should be siphoned from the bare-bottomed nurseries at least twice a day with the deficit made up with new seawater (Bull and Mitchell, 2002, p57). The sponge filters must also be cleaned often.
The benthic Pixie fry thrive on newly hatched brine shrimp (Artemia nauplii) with small, frequent feedings that provide live prey throughout the day. They seek out hitching posts from birth, meaning the fry rarely gulp air, floaters and surface huggers are virtually nonexistent, and they are largely immune from the buoyancy problems that so often plague pelagic seahorse fry.
Experienced aquarists often achieve good success rates (better than 20% survival) in rearing H. zosterae to adults using these simple methods (Bull and Mitchell, 2002, p57).
Further details on feeding and breeding and rearing your Pixies are available in Alisa Abbott’s guidebook titled Complete Guide to Dwarf Seahorses in the Aquarium, Greg.
Actually, I wouldn’t recommend keeping Banggai Cardinalfish with your dwarf seahorses. They make great companions for any of the greater seahorses, but they require a larger aquarium than the Pixies and would not do well in a three-gallon aquarium over the long-term. Flame Cardinals stay smaller than the Banggai Cardinalfish, so you could consider keeping one or two of the Flame Cardinals in your pixie tank providing you quarantine them first, but I would avoid the Banggais or Banner Cardinalfish.
It sounds like found a good fish store. It’s always a good idea to cultivate a good relationship with your LFS as long as they have reliable, knowledgeable staff. They can be very helpful in getting you started off on the right foot as an aquarist, although they may not be very experienced when it comes to seahorses.
Best of luck with your new Pixie tank, Greg!