Brine isn't the greatest food out there for fish because it hold very little nutritional value. If it is the main source of fod, make sure you enrich it by soaking it in Zoe or something like that. I feed my fish an assortment of things such as silver slides, mysis shrimp, krill, flake, nori flakes, squid, live ghost shrimp once in a while, and sometimes for a treat i give them live brine soaked in zoe for a few hours.