A testimonial - I got these cones from Matt a few weeks ago. I have them in my GBR and EBR tanks as well as with 2 of my angel pairs. Both angel pairs have laid and neither spawn fungused - a few white eggs but that was it. My koi pair has wigglers that should go free swimming in a few days and my het silver/blue pair have eggs but no fungus. They appear to be working and my fish seem to love the tannins in the water.
HTH,