diff --git a/examples/main.c b/examples/main.c
index 5127ab9ef169be30153ea2c033c17a23c8b5461f..e795e210ca84b87410e1503c063d30c9a114ae83 100644
--- a/examples/main.c
+++ b/examples/main.c
@@ -867,19 +867,19 @@ int main(int argc, char *argv[]) {
 #if defined(HAVE_HDF5)
 #if defined(WITH_MPI)
 #if defined(HAVE_PARALLEL_HDF5)
-    read_ic_parallel(ICfileName, &us, dim, &parts, &gparts, &sparts, &bparts,
-                     &Ngas, &Ngpart, &Nspart, &Nbpart, &flag_entropy_ICs,
-                     with_hydro, (with_external_gravity || with_self_gravity),
-                     with_stars, with_black_holes, cleanup_h, cleanup_sqrt_a,
-                     cosmo.h, cosmo.a, myrank, nr_nodes, MPI_COMM_WORLD,
-                     MPI_INFO_NULL, nr_threads, dry_run);
+    read_ic_parallel(
+        ICfileName, &us, dim, &parts, &gparts, &sparts, &bparts, &Ngas, &Ngpart,
+        &Ngpart_background, &Nspart, &Nbpart, &flag_entropy_ICs, with_hydro,
+        (with_external_gravity || with_self_gravity), with_stars,
+        with_black_holes, cleanup_h, cleanup_sqrt_a, cosmo.h, cosmo.a, myrank,
+        nr_nodes, MPI_COMM_WORLD, MPI_INFO_NULL, nr_threads, dry_run);
 #else
-    read_ic_serial(ICfileName, &us, dim, &parts, &gparts, &sparts, &bparts,
-                   &Ngas, &Ngpart, &Nspart, &Nbpart, &flag_entropy_ICs,
-                   with_hydro, (with_external_gravity || with_self_gravity),
-                   with_stars, with_black_holes, cleanup_h, cleanup_sqrt_a,
-                   cosmo.h, cosmo.a, myrank, nr_nodes, MPI_COMM_WORLD,
-                   MPI_INFO_NULL, nr_threads, dry_run);
+    read_ic_serial(
+        ICfileName, &us, dim, &parts, &gparts, &sparts, &bparts, &Ngas, &Ngpart,
+        &Ngpart_background, &Nspart, &Nbpart, &flag_entropy_ICs, with_hydro,
+        (with_external_gravity || with_self_gravity), with_stars,
+        with_black_holes, cleanup_h, cleanup_sqrt_a, cosmo.h, cosmo.a, myrank,
+        nr_nodes, MPI_COMM_WORLD, MPI_INFO_NULL, nr_threads, dry_run);
 #endif
 #else
     read_ic_single(ICfileName, &us, dim, &parts, &gparts, &sparts, &bparts,
diff --git a/src/serial_io.c b/src/serial_io.c
index 0d367b1cf423d0471a0f6235fa3a1c6877e9f279..3b3872762f237c4922bbc30fd866599547b23557 100644
--- a/src/serial_io.c
+++ b/src/serial_io.c
@@ -492,12 +492,12 @@ void writeArray(const struct engine* e, hid_t grp, char* fileName,
 void read_ic_serial(char* fileName, const struct unit_system* internal_units,
                     double dim[3], struct part** parts, struct gpart** gparts,
                     struct spart** sparts, struct bpart** bparts, size_t* Ngas,
-                    size_t* Ngparts, size_t* Nstars, size_t* Nblackholes,
-                    int* flag_entropy, int with_hydro, int with_gravity,
-                    int with_stars, int with_black_holes, int cleanup_h,
-                    int cleanup_sqrt_a, double h, double a, int mpi_rank,
-                    int mpi_size, MPI_Comm comm, MPI_Info info, int n_threads,
-                    int dry_run) {
+                    size_t* Ngparts, size_t* Ngparts_background, size_t* Nstars,
+                    size_t* Nblackholes, int* flag_entropy, int with_hydro,
+                    int with_gravity, int with_stars, int with_black_holes,
+                    int cleanup_h, int cleanup_sqrt_a, double h, double a,
+                    int mpi_rank, int mpi_size, MPI_Comm comm, MPI_Info info,
+                    int n_threads, int dry_run) {
 
   hid_t h_file = 0, h_grp = 0;
   /* GADGET has only cubic boxes (in cosmological mode) */
@@ -510,11 +510,13 @@ void read_ic_serial(char* fileName, const struct unit_system* internal_units,
   long long offset[swift_type_count] = {0};
   int dimension = 3; /* Assume 3D if nothing is specified */
   size_t Ndm = 0;
+  size_t Ndm_background = 0;
   struct unit_system* ic_units =
       (struct unit_system*)malloc(sizeof(struct unit_system));
 
   /* Initialise counters */
-  *Ngas = 0, *Ngparts = 0, *Nstars = 0, *Nblackholes = 0;
+  *Ngas = 0, *Ngparts = 0, *Ngparts_background = 0, *Nstars = 0,
+  *Nblackholes = 0;
 
   /* First read some information about the content */
   if (mpi_rank == 0) {
@@ -676,10 +678,13 @@ void read_ic_serial(char* fileName, const struct unit_system* internal_units,
   /* Allocate memory to store all gravity  particles */
   if (with_gravity) {
     Ndm = N[1];
+    Ndm_background = N[swift_type_dark_matter_background];
     *Ngparts = (with_hydro ? N[swift_type_gas] : 0) +
                N[swift_type_dark_matter] +
+               N[swift_type_dark_matter_background] +
                (with_stars ? N[swift_type_stars] : 0) +
                (with_black_holes ? N[swift_type_black_hole] : 0);
+    *Ngparts_background = Ndm_background;
     if (swift_memalign("gparts", (void**)gparts, gpart_align,
                        *Ngparts * sizeof(struct gpart)) != 0)
       error("Error while allocating memory for gravity particles");
@@ -740,6 +745,13 @@ void read_ic_serial(char* fileName, const struct unit_system* internal_units,
             }
             break;
 
+          case swift_type_dark_matter_background:
+            if (with_gravity) {
+              Nparticles = Ndm_background;
+              darkmatter_read_particles(*gparts + Ndm, list, &num_fields);
+            }
+            break;
+
           case swift_type_stars:
             if (with_stars) {
               Nparticles = *Nstars;
@@ -789,17 +801,23 @@ void read_ic_serial(char* fileName, const struct unit_system* internal_units,
     /* Prepare the DM particles */
     io_prepare_dm_gparts(&tp, *gparts, Ndm);
 
+    /* Prepare the DM background particles */
+    io_prepare_dm_background_gparts(&tp, *gparts + Ndm, Ndm_background);
+
     /* Duplicate the hydro particles into gparts */
-    if (with_hydro) io_duplicate_hydro_gparts(&tp, *parts, *gparts, *Ngas, Ndm);
+    if (with_hydro)
+      io_duplicate_hydro_gparts(&tp, *parts, *gparts, *Ngas,
+                                Ndm + Ndm_background);
 
     /* Duplicate the stars particles into gparts */
     if (with_stars)
-      io_duplicate_stars_gparts(&tp, *sparts, *gparts, *Nstars, Ndm + *Ngas);
+      io_duplicate_stars_gparts(&tp, *sparts, *gparts, *Nstars,
+                                Ndm + Ndm_background + *Ngas);
 
     /* Duplicate the black holes particles into gparts */
     if (with_black_holes)
       io_duplicate_black_holes_gparts(&tp, *bparts, *gparts, *Nblackholes,
-                                      Ndm + *Ngas + *Nstars);
+                                      Ndm + Ndm_background + *Ngas + *Nstars);
 
     threadpool_clean(&tp);
   }
@@ -847,6 +865,7 @@ void write_output_serial(struct engine* e, const char* baseName,
   const int with_cooling = e->policy & engine_policy_cooling;
   const int with_temperature = e->policy & engine_policy_temperature;
   const int with_fof = e->policy & engine_policy_fof;
+  const int with_DM_background = e->s->with_DM_background;
 #ifdef HAVE_VELOCIRAPTOR
   const int with_stf = (e->policy & engine_policy_structure_finding) &&
                        (e->s->gpart_group_data != NULL);
@@ -864,7 +883,13 @@ void write_output_serial(struct engine* e, const char* baseName,
   // const size_t Nbaryons = Ngas + Nstars;
   // const size_t Ndm = Ntot > 0 ? Ntot - Nbaryons : 0;
 
-  /* Number of particles that we will write */
+  size_t Ndm_background = 0;
+  if (with_DM_background) {
+    Ndm_background = io_count_dm_background_gparts(gparts, Ntot);
+  }
+
+  /* Number of particles that we will write
+   * Recall that background particles are never inhibited and have no extras */
   const size_t Ntot_written =
       e->s->nr_gparts - e->s->nr_inhibited_gparts - e->s->nr_extra_gparts;
   const size_t Ngas_written =
@@ -876,7 +901,7 @@ void write_output_serial(struct engine* e, const char* baseName,
   const size_t Nbaryons_written =
       Ngas_written + Nstars_written + Nblackholes_written;
   const size_t Ndm_written =
-      Ntot_written > 0 ? Ntot_written - Nbaryons_written : 0;
+      Ntot_written > 0 ? Ntot_written - Nbaryons_written - Ndm_background : 0;
 
   /* File name */
   char fileName[FILENAME_BUFFER_SIZE];
@@ -888,7 +913,8 @@ void write_output_serial(struct engine* e, const char* baseName,
              e->snapshot_output_count);
 
   /* Compute offset in the file and total number of particles */
-  size_t N[swift_type_count] = {Ngas_written,   Ndm_written,        0, 0,
+  size_t N[swift_type_count] = {Ngas_written,   Ndm_written,
+                                Ndm_background, 0,
                                 Nstars_written, Nblackholes_written};
   long long N_total[swift_type_count] = {0};
   long long offset[swift_type_count] = {0};
@@ -1242,7 +1268,8 @@ void write_output_serial(struct engine* e, const char* baseName,
           case swift_type_dark_matter: {
             if (Ntot == Ndm_written) {
 
-              /* This is a DM-only run without inhibited particles */
+              /* This is a DM-only run without background or inhibited particles
+               */
               Nparticles = Ntot;
               darkmatter_write_particles(gparts, list, &num_fields);
               if (with_fof) {
@@ -1293,6 +1320,46 @@ void write_output_serial(struct engine* e, const char* baseName,
             }
           } break;
 
+          case swift_type_dark_matter_background: {
+
+            /* Ok, we need to fish out the particles we want */
+            Nparticles = Ndm_background;
+
+            /* Allocate temporary array */
+            if (swift_memalign("gparts_written", (void**)&gparts_written,
+                               gpart_align,
+                               Ndm_background * sizeof(struct gpart)) != 0)
+              error("Error while allocating temporart memory for gparts");
+
+            if (with_stf) {
+              if (swift_memalign("gpart_group_written",
+                                 (void**)&gpart_group_data_written, gpart_align,
+                                 Ndm_background *
+                                     sizeof(struct velociraptor_gpart_data)) !=
+                  0)
+                error(
+                    "Error while allocating temporart memory for gparts STF "
+                    "data");
+            }
+
+            /* Collect the non-inhibited DM particles from gpart */
+            io_collect_gparts_background_to_write(
+                gparts, e->s->gpart_group_data, gparts_written,
+                gpart_group_data_written, Ntot, Ndm_background, with_stf);
+
+            /* Select the fields to write */
+            darkmatter_write_particles(gparts_written, list, &num_fields);
+            if (with_fof) {
+              num_fields +=
+                  fof_write_gparts(gparts_written, list + num_fields);
+            }
+            if (with_stf) {
+              num_fields += velociraptor_write_gparts(gpart_group_data_written,
+                                                      list + num_fields);
+            }
+
+          } break;
+
           case swift_type_stars: {
             if (Nstars == Nstars_written) {
 
diff --git a/src/serial_io.h b/src/serial_io.h
index 7d994181b135e9758a9e3a52971366c2d871f627..6badf076b8373ce2b6d5b2cd3d91a5b2f57ed8ae 100644
--- a/src/serial_io.h
+++ b/src/serial_io.h
@@ -38,12 +38,12 @@
 void read_ic_serial(char* fileName, const struct unit_system* internal_units,
                     double dim[3], struct part** parts, struct gpart** gparts,
                     struct spart** sparts, struct bpart** bparts, size_t* Ngas,
-                    size_t* Ngparts, size_t* Nstars, size_t* Nblackholes,
-                    int* flag_entropy, int with_hydro, int with_gravity,
-                    int with_stars, int with_black_holes, int cleanup_h,
-                    int cleanup_sqrt_a, double h, double a, int mpi_rank,
-                    int mpi_size, MPI_Comm comm, MPI_Info info, int n_threads,
-                    int dry_run);
+                    size_t* Ngparts, size_t* Ngparts_background, size_t* Nstars,
+                    size_t* Nblackholes, int* flag_entropy, int with_hydro,
+                    int with_gravity, int with_stars, int with_black_holes,
+                    int cleanup_h, int cleanup_sqrt_a, double h, double a,
+                    int mpi_rank, int mpi_size, MPI_Comm comm, MPI_Info info,
+                    int n_threads, int dry_run);
 
 void write_output_serial(struct engine* e, const char* baseName,
                          const struct unit_system* internal_units,