Like most fish, young fry (ponies) are born with a small yolk sac. This will provide nutrition for about the first 6-12 hours of life.
Food can be offered within the first few hours of life, but is not essential until after about 6-10 hours. Remember they have just been born and their digestive tract is very immature. It can take several days for them to be eating at the full rate.
Baby seahorse fry can consume vast numbers of newly hatched Artemia or Brine Shrimp (for large fry 10 mm onwards) and Rotifers or Copepods (which will need to be offered to some smaller fry <10 mm).
The main causes of fry death are:
Air intake: The food source, baby brine shrimp are light sensitive. The food tends to swim at the surface of the water, young fry can intake air with their food and cannot dispel this air.
This is however, avoidable. You can darken off the top and sides of your nursery tank and apply lighting to the side of the tank encouraging your fry to eat their food below the surface of the water. The diagram above is an example of a fry rearing tank.
Starvation: Starvation can be caused both by not adding enough food and by over feeding. Each baby seahorses can eat 2,000 newly hatched brine shrimp a day. Food should be added to your nursery tank at least three times per day.
You need to add enough food for your fry to eat for about 15-20 minutes (75% of the food should have been consumed). If it is not then you have added too much. They then should have some time to digest this food, about 3 hours is plenty. Only feed during daylight hours and turn off lights at night.
Poor Water Quality and Water Movement: As the stocking density of your nursery tank is high and you are continually adding foods with high fat contents to enhance growth, the water quality can deteriorate very quickly. Fry can be susceptible to bacterial infections that thrive in these conditions.
By doing regular water changes at least daily (15-30%) and keeping the tank clean of debris you can minimize the chances of bacteria building up. It is advisable to keep the nursery tank free of any gravel or sand, as a bare bottom tanks are easier to siphon.
Water flow can be critical. There needs to be enough water movement to keep the food moving past the seahorse and to keep the seahorses moving, but not too much to cause them to become tired or not be able to hitch when needed. It is also important to ensure that adequate air is supplied.
Although not necessary, a sponge filter can be added to the nursery tank to aid in water quality. This filter will need to be turned off during feed times because all the food can be sucked into the filter.
Survival rates for fry in the home aquarium vary, and can be very poor, don't get too disheartened if you don't succeed first time.