Cycling/copepods/confusion

[FaRico]

Ok so I'm in the process of cycling my tank, it's been 3.5 weeks since it got set up. My levels are doing good, ammonia has spiked and has leveled off to 0-0.5 my nitrate is at 5 ppm. Lately I've noticed that the amount of copepods is increasing, they're everywhere. When is it too early to add something to gobble these guys up? I'd love a mandarin, but I think it might be to soon. Thoughts?