Tiny critters in snail tank?

[Ekiel]

I'm planning on getting a figure 8 pufferfish as soon as my tank finishes cycling, so I decided to set up a little unfiltered 2.5 gallon tank in the meantime to breed my own snails. However, I forgot to pick up a cuttlefish bone or other calcium supplement, so I ground up some baked eggshells and added a pinch to the tank. The shells caused an offwhite, cloudy "dripping" layer in the water, which doesn't seem to be bothering the snails. A few days later, I noticed what looked like thousands of tiny white bubbles suspended in the layers, but a closer look revealed them to be moving around of their own volition. They are suspended throughout the entirety of the tank, but most densely within the cloudy layers. Does anyone know what these are, if they're harmful, or where they're from? I've been feeding the snails spinach, removing dead snails as soon as I notice them (only about 5 out of around 40) and I did 50% water change once a few days ago (It's been a week so far). Any ideas?

[puffykid]

Not sure about this one especially what they are called but I believe that they are harmless. I think they are caused because of the excess of nutrients in your tank with the extra food in there.