The most important tool is my light box ...
... which makes it very much easier to see what's going on.
Glass bowl shoved on top ...
... and sample for sorting poured in :
I have a very quick naked-eye survey to see if I can immediately remove some females. Because of their shape they're easily-identifiable and they're a little less agile than males. I use a 3ml pipette to suck them up ; a new disposable pipette is best for this. They split quite quickly down their seams and in an upcoming pic you can see I've wrapped my last one with masking tape to try to encourage it to survive until the new ones I've ordered have arrived!
Moina are strongly attracted to light, so I use cardboard under the bowl to isolate a patch of it ...
.. and a towel above to block ambient light :
Before leaving it for ten minutes to allow migration to happen, I 'dredge' the illuminated portion, using the pipette to 'blow' away any detritus that has settled there, and do a final check for females with a magnifying glass :
After ten minutes or so, by far the majority of the Moina have gathered above the light. While checking every so often with the magnifying glass, the pipetting-out of the Moina is pretty quick. A turkey-baster is even quicker but is much less efficient in terms of avoiding Cyclops. The cardboard is moved back in installments and I is scan each area just revealed for bandits :
Large male Cyclops are identifiable from Moina by their body shape (tadpole-ish vs ellipsoid-ish) density, and colour and via the differences between their locomotion (the number of jerks per second, the distance travelled per 'jerk' and their average speed!). But there appears to be a certain stage in Moina development where they are roughly the same size as Cyclops and move just as quickly, thus it's easy to get them muxed ip when working at speed! So once all the bigger Moina have been removed it's often a case of using the magnifying glass to verify what's being picked up. Mistakes still happen, though! After that it's just a matter of hoovering up the very tiny Moina - which, oddly, is the easiest part of the whole operation.
Cyclops can also be differentiated because they have an ultra-efficient forward-facing early warning system. They'll scarper when the pipette is much further away than is the case for Moina and they tend to scarper in the direction of the still-shaded bit of the bowl. By the time I remove the cardboard completely they've mostly gathered in a rather loose bunch where the last bit of shade was. Come to think of it, that's when I should use the turkey-baster. Anyway ...
Along the way Cyclops have been squirted into one container and Moina into another :
There are Moina in the Cyclops dish that have been inadvertently sucked-up, but that's OK. What's not OK is any Cyclops that may have made it into the Moina container. So unless I'm confident that it's 'clean', the Moina go back in the bowl for a final and detailed once-over with the magnifying glass.
Then they're decanted into a jar for further observation. I don't know (yet) whether this is a necessary step. Although I've removed all the Cyclops that I can see, I don't know whether there's any that were too small to see or whether there are 'loose' eggs lurking. So I'm keeping them in jars until I'm reasonably confident that they've been Cyclops-free for (say) a couple of weeks.
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