diff --git a/Gemfile b/Gemfile
index adc9b7c07..6b0586919 100644
--- a/Gemfile
+++ b/Gemfile
@@ -28,7 +28,6 @@ gem 'alto_guisso_rails', :git => "https://github.com/instedd/alto_guisso_rails",
 # libraries
 gem 'actionpack-action_caching'
 gem 'actionpack-page_caching'
-gem 'active_model_serializers'        # TODO: consider removing (one serializer)
 gem 'activerecord-import'
 gem "breadcrumbs_on_rails"
 gem 'carrierwave'
@@ -36,7 +35,6 @@ gem 'decent_exposure'                 # NOTE: pattern used in 12 out of 29 contr
 gem 'gettext', '~> 3.1.2'
 gem 'gettext_i18n_rails_js', git: "https://github.com/juanboca/gettext_i18n_rails_js.git", branch: 'master'
 gem 'ice_cube'
-# gem 'includes-count'                  # TODO: remove (only one use + breaking ActiveRecord with a frozen array)
 gem "instedd-rails" #, '~> 0.0.24'
 gem 'mini_magick'
 gem 'msgpack', '~> 0.7.5'
diff --git a/Gemfile.lock b/Gemfile.lock
index 86a7c34c2..69afeffd4 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -71,11 +71,6 @@ GEM
       erubis (~> 2.7.0)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    active_model_serializers (0.10.14)
-      actionpack (>= 4.1)
-      activemodel (>= 4.1)
-      case_transform (>= 0.2)
-      jsonapi-renderer (>= 0.1.1.beta1, < 0.3)
     activejob (5.0.7.2)
       activesupport (= 5.0.7.2)
       globalid (>= 0.3.6)
@@ -118,8 +113,6 @@ GEM
       marcel (~> 1.0.0)
       mini_mime (>= 0.1.3)
       ssrf_filter (~> 1.0)
-    case_transform (0.2)
-      activesupport
     childprocess (0.9.0)
       ffi (~> 1.0, >= 1.0.11)
     coffee-rails (4.1.1)
@@ -236,7 +229,6 @@ GEM
       activesupport (>= 4.2)
       aes_key_wrap
       bindata
-    jsonapi-renderer (0.2.2)
     jwt (2.3.0)
     knockoutjs-rails (3.5.1.1)
       railties (>= 3.1)
@@ -471,7 +463,6 @@ PLATFORMS
 DEPENDENCIES
   actionpack-action_caching
   actionpack-page_caching
-  active_model_serializers
   activerecord-import
   alto_guisso!
   alto_guisso_rails!
diff --git a/app/controllers/api/collections_controller.rb b/app/controllers/api/collections_controller.rb
index f92c0abb7..776abfc7e 100644
--- a/app/controllers/api/collections_controller.rb
+++ b/app/controllers/api/collections_controller.rb
@@ -9,7 +9,8 @@ class Api::CollectionsController < ApiController
   expose(:collection) { Collection.find(params[:collection_id] || params[:id]) }
 
   def index
-    render json: current_user.collections.includes_count(:sites).load, each_serializer: Api::CollectionSerializer
+    collections = current_user.collections
+    render_json collections_json(collections, collections.count_sites)
   end
 
   def create
diff --git a/app/helpers/api/json_helper.rb b/app/helpers/api/json_helper.rb
index ebb7fe2e5..82afa63af 100644
--- a/app/helpers/api/json_helper.rb
+++ b/app/helpers/api/json_helper.rb
@@ -10,6 +10,28 @@ def collection_json(collection, results)
     obj
   end
 
+  def collections_json(collections, sites_counts)
+    collections.each do |collection|
+      {
+        anonymous_location_permission: collection.anonymous_location_permission,
+        anonymous_name_permission: collection.anonymous_name_permission,
+        created_at: collection.created_at,
+        description: collection.description,
+        icon: collection.icon,
+        id: collection.id,
+        lat: collection.lat,
+        lng: collection.lng,
+        max_lat: collection.max_lat,
+        max_lng: collection.max_lng,
+        min_lat: collection.min_lat,
+        min_lng: collection.min_lng,
+        name: collection.name,
+        updated_at:collection.updated_at,
+        count: sites_counts[collection.id].to_i,
+      }
+    end
+  end
+
   def site_item_json(result)
     source = result['_source']
 
diff --git a/app/models/collection.rb b/app/models/collection.rb
index a06823877..5de2f2fad 100644
--- a/app/models/collection.rb
+++ b/app/models/collection.rb
@@ -36,6 +36,10 @@ class Collection < ApplicationRecord
   after_save :touch_lifespan
   after_destroy :touch_lifespan
 
+  def self.count_sites
+    Site.where(collection_id: select(:id)).group(:collection_id).count
+  end
+
   def max_value_of_property(es_code)
     client = Elasticsearch::Client.new
     results = client.search index: index_name, type: 'site', body: {
diff --git a/app/serializers/api/collection_serializer.rb b/app/serializers/api/collection_serializer.rb
deleted file mode 100644
index 1f9b1b07d..000000000
--- a/app/serializers/api/collection_serializer.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-class Api::CollectionSerializer < ActiveModel::Serializer
-  attributes :anonymous_location_permission, :anonymous_name_permission, :created_at, :description, :icon, :id, :lat, :lng, :max_lat, :max_lng, :min_lat, :min_lng, :name, :updated_at, :count
-
-  def count
-  	if object.respond_to? :sites_count
-      object.sites_count
-    else
-      object.sites.count
-    end
-  end
-end