Ignore the previous reply as to the nitrates being back up, they were, but I found out why! The Jewal sponge has its chelating agent (or whatever it is that binds the nitrate) contained within a capsule at the centre of the sponge, so I imagine only a small amount of the nitrate removal stuff was on the sponge itself. I had to massively cut the sponge down and just put the capsule in the slot in the centre. So, watch this space! hoping to see nitrates go down, and stay down!
