Rheann, what do you think blood worms and tubifex worms are? Mosquito and midge fly larvae! These are okay to have in your tank. I've never seen a parasitic midge fly larvae (not to say that they don't exist). For the most part, they go into the sediment (or substrate, in our case) and burrow in, eating detritus.
I have glass worms too, which are gnat larvae. So far, I've not found any real effective way to prevent any of these creatures from laying eggs in my tank. Even surface movement doesnt deter them. I also tried covering the tank with a fine mesh, but that made it look crappy. If there was a way you could get a screen-top, and cover the wire with fine mesh, glue it in or something, that would probably work.
The weird tube thing is probably a proboscis. It's like a drinking straw. They suck in the water and get their nutrients out, pushing the excess water out through some body opening. Best guess.
I also have the little things on the glass. Very small, no idea. They do like to eat algae though. I recently had an upcropping of brown algae in one of my tanks, and they took right care of it. Not so much with the green algae though. The Daphnia (or water fleas) have kept that in check. I've got a bloom of copepods in my axolotl tank too. Not sure what exactly they eat, but they don't bother the axolotls, so I don't bother them.
Remember, little critters in your tank are part of the normal ecosystem. They'll find their way in every time, no matter how 'clean' you keep your tank. They're good. They're mostly beneficial, such as the ones that eat algae or detritus.
If you're worried about the snails, remove them. If the little swimmy ones bother you, get a turkey baster and suck them out whenever you see them. Get a scrub brush and keep the sides of the tank free from algae, and vacuum your substrate on a regular basis. This should keep microorganisms in check.