If they are segmented, they are not planaria. They could be annelids (same group as earthworms) or insect larvae (probably a midge or other dipteran). Insects cannot stretch and contract the body, so it most likely is an annelid. If you can see eyespots, it is not an annelid. Either way, entirely harmless.
The planaria instructions in your link are for a particular species (I think it used to be called Dugesia lugubris or something like that) that is used in lab experiments; the planaria are a big group and have widely varying tolerances. And of course, lab conditions are more stringent than the conditions needed for mere survival; after all rats do just fine in sewers and trash heaps, but lab rats are kept in very clean conditions.
I've seen many planaria out and about in full sunlight, even though hiding places were available. Some giant tropical planaria are terrestrial and prowl around the forest floor.
The planaria instructions in your link are for a particular species (I think it used to be called Dugesia lugubris or something like that) that is used in lab experiments; the planaria are a big group and have widely varying tolerances. And of course, lab conditions are more stringent than the conditions needed for mere survival; after all rats do just fine in sewers and trash heaps, but lab rats are kept in very clean conditions.
I've seen many planaria out and about in full sunlight, even though hiding places were available. Some giant tropical planaria are terrestrial and prowl around the forest floor.
