My planted freshwater nano tanks have recently had an explosion of weird white spots which I haven't been able to identify. They're definitely not snail eggs, limpets, cyclops, hydra, planaria or any of the other common culprits (I've seen all of those before & this is something different). They don't seem to be bothering the fish or shrimps, but I'd still like to know what they are, just to be sure. I've never seen them move, but there seem to be more and more of them & only on the glass. My bettas aren't interested in them, and neither are the shrimps. Nothing new was added to the tank, except a different kind of fertilizer (all-in-one for shade plants) and some catappa leaves. I first noticed them after I pulled a lot of the plants and trimmed a big clump of moss - they seemed to "come out of hiding", so to speak, & have since taken up residence on the tank walls. They're rounded, no more than half a millimetre long, with little white dots inside of them and a second, smaller round part attached to the "main" body.
Any ideas on what they could be? Should I be worried, or is it just harmless plankton?