diff --git a/app/controllers/pet_states_controller.rb b/app/controllers/pet_states_controller.rb
index d6cc3193..090640ac 100644
--- a/app/controllers/pet_states_controller.rb
+++ b/app/controllers/pet_states_controller.rb
@@ -17,7 +17,7 @@ class PetStatesController < ApplicationController
 	protected
 
 	def find_pet_state
-		@pet_type = PetType.matching_name_param(params[:pet_type_name]).first!
+		@pet_type = PetType.find_by_param!(params[:pet_type_name])
 		@pet_state = @pet_type.pet_states.find(params[:id])
 	end
 
diff --git a/app/controllers/pet_types_controller.rb b/app/controllers/pet_types_controller.rb
index 392ba4fe..8fa2f524 100644
--- a/app/controllers/pet_types_controller.rb
+++ b/app/controllers/pet_types_controller.rb
@@ -70,9 +70,7 @@ class PetTypesController < ApplicationController
 				color_id: params[:color_id],
 			)
 		elsif params[:name]
-			color_name, _, species_name = params[:name].rpartition("-")
-			raise ActiveRecord::RecordNotFound if species_name.blank?
-			PetType.matching_name(color_name, species_name).first!
+			PetType.find_by_param!(params[:name])
 		else
 			raise "expected params: species_id and color_id, or name"
 		end
diff --git a/app/models/color.rb b/app/models/color.rb
index 9211aac9..dc647e99 100644
--- a/app/models/color.rb
+++ b/app/models/color.rb
@@ -21,6 +21,10 @@ class Color < ApplicationRecord
     end
   end
 
+  def to_param
+    name? ? human_name : id.to_s
+  end
+
   def example_pet_type(preferred_species: nil)
     preferred_species ||= Species.first
     pet_types.order([Arel.sql("species_id = ? DESC"), preferred_species.id],
@@ -36,4 +40,8 @@ class Color < ApplicationRecord
       nil
     end
   end
+
+  def self.param_to_id(param)
+    param.match?(/\A\d+\Z/) ? param.to_i : find_by_name!(param).id
+  end
 end
diff --git a/app/models/pet_type.rb b/app/models/pet_type.rb
index a73f510d..1ef5e884 100644
--- a/app/models/pet_type.rb
+++ b/app/models/pet_type.rb
@@ -15,10 +15,6 @@ class PetType < ApplicationRecord
     species = Species.find_by_name!(species_name)
     where(color_id: color.id, species_id: species.id)
   }
-  scope :matching_name_param, ->(name_param) {
-    color_name, _, species_name = name_param.rpartition("-")
-    matching_name(color_name, species_name)
-  }
   scope :preferring_species, ->(species_id) {
     joins(:species).order([Arel.sql("species_id = ? DESC"), species_id])
   }
@@ -116,7 +112,7 @@ class PetType < ApplicationRecord
   end
 
   def to_param
-    "#{color.human_name}-#{species.human_name}"
+    "#{possibly_new_color.to_param}-#{possibly_new_species.to_param}"
   end
 
   def fully_labeled?
@@ -136,6 +132,15 @@ class PetType < ApplicationRecord
     pet_states.count { |ps| ps.pose == "UNKNOWN" }
   end
 
+  def self.find_by_param!(param)
+    raise ActiveRecord::RecordNotFound unless param.include?("-")
+    color_param, _, species_param = param.rpartition("-")
+    where(
+      color_id: Color.param_to_id(color_param),
+      species_id: Species.param_to_id(species_param),
+    ).first!
+  end
+
   def self.basic_body_ids
     PetType.basic.distinct.pluck(:body_id)
   end
diff --git a/app/models/species.rb b/app/models/species.rb
index 9c5b1efe..8f43f05f 100644
--- a/app/models/species.rb
+++ b/app/models/species.rb
@@ -16,6 +16,10 @@ class Species < ApplicationRecord
     end
   end
 
+  def to_param
+    name? ? human_name : id.to_s
+  end
+
   # Given a list of body IDs, return a hash from body ID to Species.
   # (We assume that each body ID belongs to just one species; if not, which
   # species we return for that body ID is undefined.)
@@ -26,4 +30,8 @@ class Species < ApplicationRecord
       to_h { |s| [s.id, s] }
     species_ids_by_body_id.transform_values { |id| species_by_id[id] }
   end
+
+  def self.param_to_id(param)
+    param.match?(/\A\d+\Z/) ? param.to_i : find_by_name!(param).id
+  end
 end
diff --git a/app/views/pet_states/edit.html.haml b/app/views/pet_states/edit.html.haml
index 0f2d1b1a..4c1432c5 100644
--- a/app/views/pet_states/edit.html.haml
+++ b/app/views/pet_states/edit.html.haml
@@ -5,11 +5,11 @@
 	%li
 		= link_to "Rainbow Pool", pet_types_path
 	%li
-		= link_to @pet_type.color.human_name,
-		          pet_types_path(color: @pet_type.color.human_name)
+		= link_to @pet_type.possibly_new_color.human_name,
+		          pet_types_path(color: @pet_type.possibly_new_color.human_name)
 	%li{"data-relation-to-prev": "sibling"}
-		= link_to @pet_type.species.human_name,
-		          pet_types_path(species: @pet_type.species.human_name)
+		= link_to @pet_type.possibly_new_species.human_name,
+		          pet_types_path(species: @pet_type.possibly_new_species.human_name)
 	%li
 		= link_to "Appearances", @pet_type
 	%li
diff --git a/app/views/pet_types/show.html.haml b/app/views/pet_types/show.html.haml
index 3ba0600a..4215c16d 100644
--- a/app/views/pet_types/show.html.haml
+++ b/app/views/pet_types/show.html.haml
@@ -5,11 +5,11 @@
 	%li
 		= link_to "Rainbow Pool", pet_types_path
 	%li
-		= link_to @pet_type.color.human_name,
-		          pet_types_path(color: @pet_type.color.human_name)
+		= link_to @pet_type.possibly_new_color.human_name,
+		          pet_types_path(color: @pet_type.possibly_new_color.human_name)
 	%li{"data-relation-to-prev": "sibling"}
-		= link_to @pet_type.species.human_name,
-		          pet_types_path(species: @pet_type.species.human_name)
+		= link_to @pet_type.possibly_new_species.human_name,
+		          pet_types_path(species: @pet_type.possibly_new_species.human_name)
 	%li
 		Appearances
 
diff --git a/spec/fixtures/colors.yml b/spec/fixtures/colors.yml
index 21580a06..2404832d 100644
--- a/spec/fixtures/colors.yml
+++ b/spec/fixtures/colors.yml
@@ -10,3 +10,6 @@ robot:
 striped:
   id: 77
   name: striped
+swamp_gas:
+  id: 93
+  name: "swamp gas"
diff --git a/spec/fixtures/pet_types.yml b/spec/fixtures/pet_types.yml
new file mode 100644
index 00000000..4eafc4b8
--- /dev/null
+++ b/spec/fixtures/pet_types.yml
@@ -0,0 +1,19 @@
+blue_acara:
+  color_id: 8
+  species_id: 1
+  body_id: 123
+
+newcolor_acara:
+  color_id: 123
+  species_id: 1
+  body_id: 123
+
+blue_newspecies:
+  color_id: 8
+  species_id: 456
+  body_id: 123
+
+newcolor_newspecies:
+  color_id: 123
+  species_id: 456
+  body_id: 123
diff --git a/spec/models/color_spec.rb b/spec/models/color_spec.rb
new file mode 100644
index 00000000..371bd11a
--- /dev/null
+++ b/spec/models/color_spec.rb
@@ -0,0 +1,38 @@
+require 'rails_helper'
+
+RSpec.describe Color do
+	fixtures :colors
+
+	describe '#to_param' do
+		it("uses name when possible") do
+			expect(colors(:blue).to_param).to eq "Blue"
+		end
+
+		it("uses spaces for multi-word names") do
+			expect(colors(:swamp_gas).to_param).to eq "Swamp Gas"
+		end
+
+		it("uses IDs for new colors") do
+			expect(Color.new(id: 12345).to_param).to eq "12345"
+		end
+	end
+
+	describe ".param_to_id" do
+		it("looks up by name") do
+			expect(Color.param_to_id("blue")).to eq colors(:blue).id
+		end
+
+		it("is case-insensitive for name") do
+			expect(Color.param_to_id("bLUe")).to eq colors(:blue).id
+		end
+
+		it("returns ID when the param is just a number, even if it doesn't exist") do
+			expect(Color.param_to_id("123456")).to eq 123456
+		end
+
+		it("raises RecordNotFound if no name matches") do
+			expect { Color.param_to_id("nonexistant") }.
+				to raise_error ActiveRecord::RecordNotFound
+		end
+	end
+end
diff --git a/spec/models/pet_type_spec.rb b/spec/models/pet_type_spec.rb
new file mode 100644
index 00000000..dbd3b3a6
--- /dev/null
+++ b/spec/models/pet_type_spec.rb
@@ -0,0 +1,41 @@
+require 'rails_helper'
+
+RSpec.describe PetType do
+	fixtures :colors, :species, :pet_types
+
+	describe '#to_param' do
+		it('uses color and species name when possible ("Blue-Acara")') do
+			expect(pet_types(:blue_acara).to_param).to eq "Blue-Acara"
+		end
+
+		it('uses color ID for new colors (123-Acara)') do
+			expect(pet_types(:newcolor_acara).to_param).to eq "123-Acara"
+		end
+
+		it('uses species ID for new colors (Blue-456)') do
+			expect(pet_types(:blue_newspecies).to_param).to eq "Blue-456"
+		end
+
+		it('uses color ID and species ID when both are new (123-456)') do
+			expect(pet_types(:newcolor_newspecies).to_param).to eq "123-456"
+		end
+	end
+
+	describe ".find_by_param!" do
+		it('looks up by species and color name ("Blue-Acara")') do
+			expect(PetType.find_by_param!("Blue-Acara")).to eq pet_types(:blue_acara)
+		end
+
+		it('looks up by color ID for new colors ("123-Acara")') do
+			expect(PetType.find_by_param!("123-Acara")).to eq pet_types(:newcolor_acara)
+		end
+
+		it('looks up by species ID for new species ("Blue-456")') do
+			expect(PetType.find_by_param!("Blue-456")).to eq pet_types(:blue_newspecies)
+		end
+
+		it('looks up by color ID and species ID when both are new ("123-456")') do
+			expect(PetType.find_by_param!("123-456")).to eq pet_types(:newcolor_newspecies)
+		end
+	end
+end
diff --git a/spec/models/species_spec.rb b/spec/models/species_spec.rb
new file mode 100644
index 00000000..5f014357
--- /dev/null
+++ b/spec/models/species_spec.rb
@@ -0,0 +1,34 @@
+require 'rails_helper'
+
+RSpec.describe Species do
+	fixtures :species
+
+	describe '#to_param' do
+		it("uses name when possible") do
+			expect(species(:acara).to_param).to eq "Acara"
+		end
+
+		it("uses IDs for new species") do
+			expect(Species.new(id: 12345).to_param).to eq "12345"
+		end
+	end
+
+	describe ".param_to_id" do
+		it("looks up by name") do
+			expect(Species.param_to_id("acara")).to eq species(:acara).id
+		end
+
+		it("is case-insensitive for name") do
+			expect(Species.param_to_id("aCaRa")).to eq species(:acara).id
+		end
+
+		it("returns ID when the param is just a number, even if no record exists") do
+			expect(Species.param_to_id("123456")).to eq 123456
+		end
+
+		it("raises RecordNotFound if no name matches") do
+			expect { Species.param_to_id("nonexistant") }.
+				to raise_error ActiveRecord::RecordNotFound
+		end
+	end
+end