It's normal - they seem to restrict airflow a bit and aren't up to quality. Received a couple of these in a 6 pack, the valve part read was poorly placed or not fully connected. With the other devices, I've found that they restrict airflow a little more than other check valves I've used.
KEDSUM Battery Aquarium Air Pump: Ultra-Quiet Rechargeable Fish Aerator with Dual Outlets - Ideal for Fish Tanks, Outdoor Fishing, Fish Transportation, and Power Outages
35 Review
KEDSUM 330GPH Ultra Quiet Submersible Pump With High Lift And Grounded Power Cord - Ideal For Fish Tanks, Ponds, Aquariums, Statuary, Hydroponics - Includes 3 Nozzles And 1500L/H Water Flow
39 Review
πΏ Enhance Your Freshwater Fish Tank with Greenpro Java Fern on Driftwood Live Aquarium Plants
27 Review
KEDSUM Quiet Rechargeable Battery-Operated Aquarium Air Pump With Dual Outlets - Perfect For Fish Tank, Outdoor Fishing, Transport, And Emergencies
28 Review
π Tetra No More Algae Tablets 8 Count: Effective Algae Control for Aquariums
8 Review
π 1-Count Container of Glass Aquarium API Algae Scraper
4 Review
π§Ό Efficient Cleaning Made Easy: Mag-Float-30 Small Glass Aquarium Cleaner with Convenient Scraper Option
8 Review
FISH PROS Fine Mesh Handle
3 Review