teeny tiny mysid shrimp (maybe)

[asylumdown]

My overflow boxes are chalk full of these itty bitty little shrimp like things that swim in really fast zig zaggy like circles. I just found a sizeable colony of them in my skimmer chamber as well and upon closer inspection they look like the tiniest of mysis shrimps.

I have no idea how they come to be in my tank, I break all my corals off their rocks/bases and dip them all in solutions that should kill them, and I haven't added any live-rock for almost a year and a half. They certainly weren't there last December when I was dealing with aiptasia and spent hours looking in my overflows with a flashlight. I don't think I've added anything that something so conspicuous could have hitchhiked in on since.

Is this a good or a bad thing?