twig catfish fry would eat Spirulina Sticks because they quickly turn to a soft mush. However, it may be necessary to start the fry out in water only about 6 inches deep so they will be in closer proximity to the food.
I would use an air stone and a sponge filter connected to a power head which has an adjustable flow rate so they have a current but not to strong. The sponge filter will collect bits of the Spirulina mush on the sponge surface where the fry may do most of their feeding. I would also provide a thin layer of fine silica sand on the bottom, pieces of wood and some broad leaved stemmed plants like Hygrophila or Ludwigia. Bits of Spirulina mush will settle on the leaves and provide the fry with more available feeding surface area.