I'm in agreement, blue stripes can take adult brine shrimp with ease. They are surprisingly vicious considering their small mouth size. They can be trained to eat frozen food pretty easily too.
If you are okay hatching brine shrimp out, the florida pug nose pipefish is another good choice. One of my favorites, they stay quite small. They are hard to come by though, unless you get them from a collector in florida (that knows what they're doing).