That's very interesting @mistergreen and @Gerald. I wasn't aware of these facts. They definitely move like snakes/eels, so I suppose that they are indeed microworms. And they're a little "stinky", unlike Grindal worms which practically have no distinctive smell
In some of my boxes they pushed Grindal worms to the sides and microworms occupy almost whole surface area.
In other boxes they co-exist side by side, similarly to the attached picture.
Any idea how could I increase numbers of Grindal worms and suppress microworms? I don't want to wipe them, just have at least 1:1 ratio.
Btw. I'm feeding them with crushed oatmeal flakes, usually amount which they consume within 1 day. Occasionally I inadvertently overfeed them and have to remove spoiled flakes after 3 days or so. Not sure if this overfeeding could be causing increased number of microworms. Today I started another culture with as "clean" Grindal worms as I could obtain, but I'm sure that some of microworms got into the substrate (pure coco peat), so not sure that it will make any difference.