Review on 🐠 Premium ALEGI 4pcs Small Aquarium Bio Sponge Filter: Ideal for 5 Gal, 10 Gal, 20 Gal Breeding Fry Betta Shrimp Fish Tank! Includes Suction Cups and Check Valves. by Lalaine Fernandez

They do what they were made to do. I had a small problem when I connected everything. I couldn't get any air out even though everything was on, air pump, attached hose, check valves in the right direction etc. As I understood the problem was in the check valve. When I tried to blow through it, no air came out. The doors that open stick together. I took a small item and put it inside and pushed it to the doors and they opened. worked fine afterwards.