I have a mandarin that I've had for just over a year, he does eat the amphipods in my tank, as well as copepods. (My tank has tons of both)My mandarin may be the happy exception though, as he also readily eats any and all of the variety of foods I feed. Weirdly, he especially loves bloodworms, typically a FW food, but my fish readily eat them, so I give them once a week or so. I do use a syringe to "target" feed the mandarin, making sure there is food delivered to wherever he is as the other fish are faster feeders.