Iron sol'n; 10,000 ppm; stable at seawater pH. Increases iron, arguably the most important trace element to photoautotrophs (including zooxanthellae), in recirculating seawater systems, particularly those employing  turf scrubber filtration. Required for photosynthesis, electron transport, nitrogen fixation, antioxidant activity, pigment production, and reduction of nitrite, nitrate, and sulfate. 1 drop (0.05 mL) per 2,365 gal. (8,953 L), once daily to maintain NSW value for S=35. 10,000 ppm iron, derived from chelated iron (anhydrous, USP).