Review on Lee's 🚮 Carbon Cartridge, Effortlessly Disposal-friendly by Amy Meyer

They work fine. They can be opened, refilled with charcoal (flushed before re-installation) and resealed when you want to save money. Or you can clean them a limited number of times depending on the amount of toxins, heavy metals, etc. in the aquarium water. Rinse well in warm water. After rinsing, bring the cartridge to your ear. If you don't hear a crackle/pop, the cartridge or charcoal needs to be replaced as the charcoal will no longer activate and remove toxins from the water.