I would recommend going with the eheim hoses if you can find them, they are much better than the hoses you can find at your local hardware store. The fittings are actually metric.
Input tubing (I.D./O.D.) - 25/34mm or 1.00/1.34"
Output tubing (I.D./O.D.) - 16/22mm or 0.625/0.875"