The spirulina brine shrimp are fed vitamin fortified algae (a certain type), vs the reg brine shrimp which are not. Its supose to be healthier for the fish.
I would give them a variety of both veggies and meaty foods, like one day give them shrimp, copods, etc and the other spirulina flakes, or any other veggie food. I keep that routien of meaty foods on one day and the other on others w/ all of my fish,
FW and now sw (trying to get nemo on my sced anyways, there are so many copods in the tank hes going crazy eating all the time).