diff --git a/src/survivor_selection/survivor_selection_methods.py b/src/survivor_selection/survivor_selection_methods.py
index 0aaa574..ce88362 100644
--- a/src/survivor_selection/survivor_selection_methods.py
+++ b/src/survivor_selection/survivor_selection_methods.py
@@ -6,33 +6,37 @@ class Survivor_Selection:
     def fill_in_best(ga):
         """Fills in the next population with the best chromosomes from the last population"""
 
-        # add in chromosomes starting from
-        # the first chromosome in the population
-        # until the next population is full
+        needed_amount = ga.population.size()-len(ga.population.next_population)
         ga.population.append_children(
-            ga.population.get_chromosome_list()[:ga.population.size()-len(ga.population.next_population)]
+            ga.population.get_chromosome_list()[:needed_amount]
         )
 
 
     def fill_in_random(ga):
         """Fills in the next population with random chromosomes from the last population"""
 
+        needed_amount = ga.population.size()-ga.population.total_children()
+
         ga.population.append_children([              # add in chromosomes
             random.choice(                           #     randomly
                 ga.population.get_chromosome_list()  #         from the population
-            )                                        # until the next population is full
-        for n in range(ga.population.size()-ga.population.total_children())])
+            )                                        # 
+        for n in range(needed_amount)])              # until the next population is full
 
 
     def fill_in_parents_then_random(ga):
         """Fills in the next population with all parents followed by random chromosomes from the last population"""
 
-        ga.population.append_children(               # add in chromosomes
-            ga.population.get_mating_pool()          #     from the mating pool
-        )                                            #
+        needed_amount = ga.population.size()-ga.population.total_children()
+        parent_amount = max(len(ga.population.get_mating_pool()), needed_amount)
+        random_amount = needed_amount - parent_amount
+
+        ga.population.append_children(                       # add in chromosomes
+            ga.population.get_mating_pool()[:parent_amount]  #     from the mating pool
+        )                                                    # 
 
         ga.population.append_children([              # add in chromosomes
             random.choice(                           #     randomly
                 ga.population.get_chromosome_list()  #         from the population
-            )                                        # until the next population is full
-        for n in range(ga.population.size()-ga.population.total_children())])
+            )                                        # 
+        for n in range(random_amount)])              # until the next population is full