diff --git a/src/music_box_conditions.py b/src/music_box_conditions.py
index 7a295613..2ce3735d 100644
--- a/src/music_box_conditions.py
+++ b/src/music_box_conditions.py
@@ -56,6 +56,10 @@ def from_UI_JSON(cls, UI_JSON, species_list, reaction_list):
 
             species_concentrations.append(SpeciesConcentration(species, concentration))
 
+        for species in species_list.species:
+            if not any(conc.species.name == species.name for conc in species_concentrations):
+                species_concentrations.append(SpeciesConcentration(species, 0)) 
+
         # Set initial reaction rates
         reaction_rates = []