Most people do not really understand what is involved, nutritionally speaking, with hatching and feeding BBS. I usually suggest that people read the following article by Dr. Rob Toonen, a marine biologist, which was published in the Advanaced Aquarist. I was fortunate enough a few years ago to exchange a number of Emails with Dr. Toonen on this subject.
The article deals with feeding BBS and adult brine shrimp to sw fish. The main difference between feeding brine shrimp to sw and fw is the nature of enrichment needed for the fish. Feeding the Brine requires the addition of HUFAs for sw but not for fw when doing enrichment. However, when feeding both fw and sw fish, the brine must be enriched. When it comes to BBS there is a very very short window when they have any real nutritional value for fw fish. This is the key to understanding using BBS for fry and small fish:
When Artemia nauplii first hatch (Instar I), they do not have a complete gut, and it is not until they develop to Instar II that the baby brine start to feed. The time of development to Instar II depends on a variety of factors (most importantly temperature, but also salinity), but occurs within 6 to 30 hours after hatching. At 28°C (roughly 82°F) it takes about 8 hours for the newly hatched nauplii to begin feeding, and as the temperature drops, that time becomes much longer. As soon as the nauplii hatch, they begin to digest their yolk and become less nutritious with time after hatching, however, once they reach the second instar, they can begin to feed, and you can enhance their nutritional value
from
http
/www.advancedaquarist.com/2004/1/inverts
What this means is that, once they hatch, BBS are on a rapid slide to having almost no nutritional value when fed to fish. It is the yolk sac they begin using up right away that would provide the nutrition for the fish. In addition, they start to grow right away. If one does not feed them to fish etc. within a few hours of hatching, the fish will love them but will derive minimal nutritional benefit from them. And if one waits until the second Instar stage to enrich them, they may become too large for fry sized fish to eat.
When I was dealing with angelfish spawns I used to run two setups for hatching BBS so that I was always getting freshly hatched BBS. The were started about 12 hours apart. There is also a product available called a Hatch and Feed. This actually goes inside a tank and is powered by an external air pump. There is a natural sw and fw barrier so that the brine hatch in the sw part and then the design is such that they move into the fw part and from there are able to swim out into the tank. They are motivated to do this because BBS are attracted to light and the Hatch and Feed is tinted gray except for a cap with holes in it that allows them to swim out and into the tank. The external lighting shines through the holes which attracts the shrimp and from there out they go.
The problem with this device is, while it produces a steady stream of freshly hatched bbs, it is not a huge number all at once. I needed a lot of them and even with two devices on a small tank, I could not keep up with many 100s of angelfish fry. However, for smaller numbers of fry/fish they work pretty well and are easy to use.
Here is a series of videos for the in tank Hatch and Feed.
[media]https
/www.youtube.com/watch?v=O17MkKMCl-Y[/media]
