Try Boyds Chemi-Pure elite and/or Purigen...
I'm skeptical that the Pura product releases any more iron into the water than any other product. In addition, iron is depleted very rapidly in our tanks.Iron oxide hydroxide can be completely amorphous (having randomly arranged ions), completely crystalline (with an ordered arrangement of ions), or something in between. In nature it can take a variety of different crystalline forms, including goethite, lepidocrocite, and limonite. The detailed chemistry of these materials is beyond the scope of this article, but in short, all of the commercial GFO's sold to aquarists are comprised of a solid of Fe+++ and OH- and O-- ions