Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
No sand has high CEC. By its very definition it cannot.
Cationic Exchange Capacity is only possible on extremely small particles. Small enough to carry a charge. Clay particles and Humus particles are in this size range.
Clay can bind together to become larger bits without losing the ionic properties.
Materials like Montmorillonite clay make good aquarium substrates for this reason.
certain brands of Kitty Litter (do a search here, and read which ones hold up and which turn to mush)
Safe-T-Sorb (available at Tractor Supply and other places)
Turface (a sports field material available at irrigation and related stores like John Deere, Ewing and others)
ADA product line also has pretty high CEC.
Some peat moss is fairly good at it.
Why not just build a sand area into the tank without swapping out all the substrate? Look at some of the 'scapes with a sand path, or area at the front.