chelate or sequester

[Jay diesel]

Can you comment on products that chealate metals, like edta based materials vs products that sequester and remove metals with filtration?

[waterbear]

All chelating agents are sequesterant but not all sequesterants are chlelating agents...chelating compounds have a ring structure (this is just what it sounds like, the atoms are arranged in a ring shape except it is broken and not complete so it can 'clamp' onto the metal ions...sequesterant might or might not have one, but they both will 'deactivate' a metal ion so it does not react with other substances in the water.
EDTA is not an effects chelating agent because it is easily broken down by chlorine. Citric acid also does not play well with chlorine. The preferred sequestrant is HEDP.
NONE of them remove the metals by filtration (no matter WHAT the marketing literature says). They chemically deactivate the metal ions for a period of time so they stay dissolved and do not precipitate out or otherwise stain or cause problems. They ONLY way to remove metals is to either cause them to precipitate out (stain) the filter medium and then change the medium, dissolve them all in the water and do a complete water change, or use an ion exchange filter medium (such as CULator, which might or might not work. Jury is still out but it does seem promising.)