Anyone have their hemets spwan?

[onthefly]

Last night, while looking at my tank (in the dark with a flashlight) I noticed hundreds of small color-less (opaque gray) critters in my tank. They looked like small (1-2mm) fish, but I was wondering if they could be crab larvae? See below for a list of my inhabitants? This morning, there was no evidence of the "orgy/rave" in my tank. Maybe they: 1) were a great breakfast for my fish 2) are in the substrate or 3) or were sucked into the filter!

[sjpresley]

My guess is that they are copepods. In general, all fish stages are active during the same times (i.e., you have diurnal fish and so would their offspring be). Copepods are fast agile swimmers and in the absences of predators are active all day. However, in a small container will a lot of predators they would be more active at night when the predators are less effective.