so should i switch brands? i was planning on getting hikari brine and pe mysis once it fully eats frozen brine.
Mandarins have tiny mouths - feed them accordingly. I have had no luck with PE Mysis myself unless it's finely chopped (and even then, my 2 don't really eat it much).
I have a M+F pair from ORA...they don't get along together (but are housed with a divider for now). I used to let them fight it out for a bit to see if it would stop and I can honestly say from my observations of who was the aggressor at the time: they need to feel comfortable to eat prepared foods.
As for their favorite foods, it's hands down Nutramar Ova, but they both eat masago as well (Capeline Roe). The latter can be bought at an Asian market for cheap - I have a 1lb tub I bought for only $20! Unfortunately, this isn't good for a staple as it's overly fattening. My guess is that they eat these foods so readily because Mandarin Dragonets have a natural diet that includes fish eggs.
The male also really likes bloodworms, but has trouble keeping them down unless they're chopped a bit. The female will eat pellets but not enthusiastically. They both also eat cyclopeeze really well (I had to train them onto this), which I think is a healthy staple while I'm getting them over to mostly pellet.
I have a couple pieces of advice as far as general feeding goes: train your mandarin to eat in a certain area and they'll learn to eventually. Read up on "Mandarin Diners" - that's how I really got my 2 to eat without polluting the tank with massive feedings. They also get spot fed now and then (1-3 times per day now). Make sure you turn the flow off when you do though.
In general, mandarins *are* hard to train: it can take a while for them to recognize something as food. I'm still having trouble with my 2 with pellets and have spent a lot of money on food for them. We get them in often at the fish store I intern at, and it's generally the same: nutramar ova is the favorite. If he's spitting it out, I think he'll take it eventually...keep trying!