In my windowfarm I have chosen to use clay pellets. Before putting the pellets in the bottles I washed them to get rid of all the dust, but apparently not thoroughly enough. Dust from the clay have gradually come loose and clogged the system.I don´t know if there are different qualities of clay pellets. But I have bought different brands in different price ranges and there has always been with both dust and small pieces of broken pellets.
Now that I bought new pellets, I have washed and washed and washed to be sure to remove all loose particles.
When you think you’ve washed enough, wash some more.