Strange Creatures In Tank.

[rob158]

Hi,
There are some strange little things in my tanks I was wondering if you know what they are? The photos are under a microscope at x 150 or so.
The first one is a free swimming thing, at first I thought it was a larger infusoria as it looked like it was moving in the same way. under the scope you can see it has legs and swims using them like a brine shrimp. You can also see it is carrying eggs in the same way a water cyclops would however under the scope it does not look are move like one.
The second is I think is some sort of bryozoa but these are all spaced out from each other and don't seem to be forming any type of colony. These are stuck to the sides of the tank. As you can see from the pictures these are able retract into their 'shell' to hide.
 
 

IMG_0553 by Robert wright., on Flickr
 

IMG_0560 by Robert wright., on Flickr
 

IMG_0556 by Robert wright., on Flickr

 

[bluesword23516]

I have had the first one in my tank before! I could never figure out what it was either!  It decided to grow in my filter compartment, it was weird. I got it our as soon as possible.  It was really gross! 

 

[DerpPH]

I think they are some type of isopod or something. They come up in fish tanks with no fish. They are a primary food source of fish though