I've been following the TFP methods for a while, but when i bought my pool i had no clue. Because of that, they installed the Nature 2 with the inline chlorinator for tabs, plus the metal insert. I replaced the metal thing once (really expensive) then started using the PROPER METHODS taught here so I never replaced the second one. I assumed the metal had "run out" but lately decided it's not worth chancing it. I took out the insert, busted open the bottom of the plastic, and removed the metal balls. Put the empty piece back and all seems fine. Just wanted to share...