What width of tyre can I fit?

AllezAllezAllez

I was looking at the Planet X XLS and noticed it has "Mach 1 820 Rims On Deore M525 29er Wheelset / 29er / Black"...if I wanted to use slick tyre's what is the smallest width I can use?

For a pure road ride could I use a standard 700 x 23c?

Escadrille Ecosse

I'd go with 25's, but I ride them over 23's anyway because they are a lot more comfortable. There is an argument that they are faster too;

http://www.bikeradar.com/gear/article/bicycle-tires-puncturing-the-myths-29245/