Wierd little wiggly white things - what the heck are they?

[mk1151]

So my water has been cloudy for a few days, and today I noticed a few types of things clinging to the glass

The first looks like a baby white hermit crab - I can actually see a tiny white shell with an almost translucent creature at the top.

The second is in a group in almost a spider web formation - I think these are snail eggs

The third are scattered all over the tank glass - they're like little squirmy worms

The fourth are spheres with little arm things radiating from the center and they don't move

I only have snails and hermit crabs in the tank - it's just about cycled as of today. Do I need to add a fish or two to eat these things? Should I clean the tank glass?

Thanks!

[Marinefish]

The first are amphipods-good. The third are some kind of worm-good til 4", then may be bad. The fourth are micro serpent stars-good cleaners.