Feedy.io is described as 'Best alternative to Agar.io'. There are more than 50 games similar to Feedy.io for a variety of platforms, including Online / Web-based, Android, iPhone, iPad and Android Tablet. The best alternative is Agar.io, which is free. Other Feedy.io like games are Spore (Paid), Slither.io (Freemium), Osmos (Paid) and Thrive (Free, Open Source).
You start as a small Cel, and try to get bigger with eating others who are trying to do the same. How long can you survive? Develop your Agar.io skills and try to survive as much as you can and try to be the biggest.