Second this - I have a pair of Biota mandarins that are thriving in my 20 gallon. They eat mysis from the water column and TDO C1 pellets. I also put a bottle of 5280 pods from AlgaeBarn in every 4 weeks. TDO pellets are by far the best way to get them eating other types of food - you also can’t have aggressive fish in your tank as they will not deal with that type of stress well.My Biota mandarin is about year old and doing great. Eats pellets and frozen like a champ. Even comes to the surface to grab pellets when the auto feeder comes on. great little fish.
I’m phasing out frozen baby brine - it has done a number on my nitrates as most end up getting caught in filter sponges. If I were you I’d work on getting TDO pellets going long term - I dont think baby brine alone is going to be nutritious enough, but glad it’s eating for ya either way!