Nikon d3100 lens help? - 2

Okay
I want a fisheye lens for my nikon d3100
do I need an adapter for my lens?
are there any type of fisheyes I wouldn't need an adapter for?

Http://www.bhphotovideo.com/c/search?ci=274&N=4293344976+4294185277+4277998923+4294949229
all of them will fit the D3100. None of them will autofocus, however.
I suggest Nikon or Tokina.

Have a look at Precision Design 0.25x Super AF Fisheye Lens
All glass lens elements; Exceptionally large depth of field
Reduces your lenses focal length by an amazing.25X; Offers attention-grabbing and distinctive perspectives
Optimized to work with almost any lens with a minimum focal length from 18mm to 50mm
Includes set of adapter rings to work with 52mm, 55mm, 58mm & 62mm filter diameters
Can offer ultra wide angle, diagonal fisheye and circular fisheye images; Especially useful for real estate or shooting in confined spaces