Brine Shrimp do have very little nutritional value for the horses unless they are just hatched. The egg sack makes baby brine shrimp nutritional for the first 24 hours after hatching, but my adult seahorses don't even look at baby brine shrimp. I have had these janitor shrimp (which are close to ghost shrimp) in my tank for about a month now and those that have not been eaten actually help clean the algae off my rocks. I sprinkle vibrance from ocean rider in my water once a week and you can actually see the vitamin powder in the shrimps belly (vibrance is red). Once they lose the red color in their abdomen I add a little more powder to help make the ghost "janitor" shrimp more nutritional, and I also feed spirinula enriched mysis/brine cubes. I would think a full belly is better than starvation even if what you are feeding isn't perfectly nutritional. And the frozen food fed daily by someone near you will help keep them on their frozen diet and get them the vitamins the live food might be lacking. I would not suggest feeding your horses live food only during the period you are gone, but it would help to give your horses a tasty treat and help ensure they don't go hungry if for some reason someone can't make it to your house one night