As a general rule, you cannot count on adult Pixies or dwarf seahorses to readily eat frozen baby brine shrimp or any other frozen foods consistently. Dwarf seahorses are pretty lazy hunters. They like to anchor their tails to a convenient hitching post and wait for their food to come to them, rather than chasing after potential prey. In most cases, attempting to get them to eat frozen food just results in polluting your aquarium.
It can sometimes be done with lots of time, patience, and perseverance, and it isn’t really as difficult as most folks imagine to train adult dwarves to eat frozen foods IF you have a role model to teach them (Liisa Coit, pers. com.). Zulus, tubers, barbs, young erectus, etc. all make great teachers, and most adult zosterae will learn to take bits of frozen mysis or sometimes the frozen form of Cyclop-eeze readily enough with such role models to show them the way. But some dwarves just don’t get it and never learn to eat frozen fodder and, in my opinion, it’s just not worth the effort of trying to train any of them.
Why? Because in most cases training adults to eat frozen food by no means frees the dwarf seahorse keeper from the need to hatch out huge amounts of baby brine shrimp every single day. Think about it. Anybody who keeps any amount of dwarf seahorses always has zosterae fry on his hands. The fry need copious amounts of newly hatched Artemia nauplii daily anyway, so it’s simply easier and more efficient to hatch out enough bbs for the adults at the same time. Many hobbyists prefer to raise dwarf fry in the same tank as their parents, so maintaining an adequate feeding density of Artemia nauplii for the newborns automatically assures that the adults are equally well fed. For me, there’s just no percentage in spending a lot of time and effort trying to train adults to eat frozen food when I still have to keep a battery of brine shrimp hatcheries cranked up full blast for the babies anyway.
In short, Jamie, if you don’t intend to breed your Pixies, then you might consider training them to eat the Ocean Nutrition Instant Baby Brine Shrimp, but otherwise it’s probably not worth your time and trouble. If you do give it a try, I would include some form of aeration or water movement to keep the Instant Baby Brine Shrimp suspended in the water column within reach of the dwarf seahorses. Once it settles to the bottom, they are extremely unlikely to leave their perches and snick up nonmoving food from the bottom.
Best wishes with all your fishes, Jamie!