I think I would start with the following in either a 3 or 5 gallon tank. Air to keep the water moving so it doesn't get stagnant.
Copepods:
Parvocalanus crassirostris is recognized by top aquaculturists and aquarium breeders as one of the best live foods for the smallest and most difficult of the marine fish larvae due to the small size of the nauplii.
This small pelagic copepod is rich in essential fatty acids and provides good nutrition for developing larval fish. In aquariums, the small size is optimum for capture by the finest filter feeders such as feather dusters and Christmas tree worms, SPS corals and sponges.Tropical marine species. Herbivorous, Eats microalgae, Phytoplankton. Reproduces by scattering eggs.
Live Phytoplankton is intended for use as a highly nutritious copepod live food.
I would also have rotifers as well. Probably this set here. Check out the link.
https://reedmariculture.com/support_rot ... turing.php