There isn't anything as easy as brine shrimp, at least that is normal to salt water.
I raise brine shrimp and mysids for resale, and mysids are a lot more work for 1/1000th the numbers.
What ever you decide on however, it should only be a part of your feeding program as variety is much more likely to supply all the needs of your fish.
Contrary to what many people think, live brine shrimp are not nutritionless.
When first hatched, before the egg sack is used up, the brine are low in protein, but are very high in the fatty acids that our inhabitants need. As the sack is consumed by the shrimp, the fatty acid levels go down rapidly and the protein levels increase so that cultured live brine shrimp produced from Great Salt Lake cysts, have protein levels based on dry weight, in the high 50% range, and wild caught ones can be over 60% protein. While the fatty acid content of adults is low, the brine can be gut loaded with Selco/Selcon type products to restore the levels of fatty acids with adults taking only about 1 hour to gut load.
They can also be gut loaded with spirulina which will boost the protein levels even more.
The United Nations article for Live Foods for the Aquaculture Industry, edited by the Artemia Reference Centre at the University of Ghent, provides the most complete information on Artemia (brine shrimp) available on the internet.
The section on nutrition is found at:
NUTRIONAL PROPERTIES OF ONGROWN ARTEMIA
The complete article on Artemia can be found at:
ARTEMIA
The complete article on Live Foods for the Aquaculture Industry can be found at:
Manual on the Production and Use of Live Food for Aquaculture