I would wait until my tank was at least a year old. You can tell. There are tons, and within several months of adding my mandarin, it was decimated. I keep a refugium and I supplement his diet with zooplankton, rotifers, enriched brine shrimp, baby brine shrimp, mysis (both frozen and live).
I also put a small 5 gal tank together with calurpa when I discovered these shrimp (not scuds, ampods or copepods) making tons of babies in my HOT filter. (I keep it off unless I am due for a water polish). It turned out to be a colony of mysis, and these like lower light so I used an old 5 gal bow tank and halimedia, and calurpa clippings and every so often I drop in some phytoplankton. I just scoop out a bit and drop in for my seahorses and my mandarin.
Ray