Where to stay near Fderik has an honest one-word answer: mostly, you do not. This is a small desert mining outpost in northern Mauritania's iron-ore country, without a formal lodging scene set up for outside visitors. Anyone traveling this route plans their actual stays around Zouerat, the mining town a short distance away that serves as the region's real base, and Nouadhibou, the coastal city at the other end of the route.
Zouerat, headquarters of Mauritania's SNIM mining operation, has the more practical lodging: a small run of simple guesthouses and basic hotels built for mining personnel and the occasional traveler passing through en route to or from the iron-ore train, which runs between Zouerat's mines and the port at Nouadhibou. Nouadhibou, being a genuine coastal city, carries the wider range - guesthouses through to a modest mid-range tier serving fishing industry visitors and the small stream of travelers riding the ore train for its own sake. Neither town offers anything resembling a premium resort tier; this is a working corridor, not a leisure one. Travelers who plan to break the corridor into stages sometimes overnight in both towns, using Zouerat for the mining and rail context and Nouadhibou for its fishing port and coastal air links.
Book Zouerat or Nouadhibou lodging a few days ahead if your dates line up with the iron-ore train's irregular passenger car schedule, since travelers timing a ride often cluster around the same departures. Expect cash to be the norm and confirm any arrangement directly with the guesthouse, since formal booking platforms have little reach out here. The desert heat is intense for much of the year, and the cooler months, roughly November through February, are the more comfortable window for the exposed waits that come with train travel through this corridor. Mobile phone coverage is patchy along stretches of the corridor, so confirming pickup times and lodging details before setting out is worth the extra care.