Celtic boss Ronny Deila says keeping his best players will take priority over acquisitions in the transfer window.
Chelsea striker Fernando Torres is understood to be set for a return to Atletico Madrid, according to Sky sources.
The well-travelled 32-year-old has penned a contract until summer 2014 with the Andalusian outfit.
Sporting director Juan Carlos Cordero told club website www.granadacf.es: "We spent time negotiating with Zaragoza for Aranda. There is a transfer fee of 500,000 euros.
"We have signed him for this season and one more. He's a player we wanted and we needed. Has has many attributes that will help Granada."