Review on Marina Filter Ceramic Cartridge 9 Count by Vera Hernandez

They advertise that these filters need to be replaced every 2-3 weeks but DON'T FOLLOW WHAT THEY DO! If you love your fish you need to keep the filters on for as long as possible or you will lose colonies of ammonia/nitrite neutralizing bacteria with them. If the cartridge is clogged, simply clean it and flush with waste water (never tap water). If you have a fully used tank, you should only replace one cartridge at a time if it really needs to be replaced.