Chemical filtration is the third filter stage and removes molecules that mechanical + biological can't catch. Activated carbon (GAC): removes organic compounds (DOC), tannins, medications, odors. Replace every 3-4 weeks - exhausted carbon stops adsorbing. GFO (Granular Ferric Oxide): removes phosphate (PO4). Place in fluidized media reactor. Replace when media stops decreasing PO4 levels. Purigen (Seachem): regenerable synthetic adsorber - removes DOCs, tannins, ammonia. Soak in 1:1 bleach/water 24h, dechlorinate thoroughly to regenerate. Cuprisorb: removes residual copper after QT treatment. Caveat: chemical filtration removes medications too - always remove during dosing.
Reviewed by the Fast Aquatics husbandry team · Updated May 2026
Chemical filtration uses adsorbent media (activated carbon, GFO, Purigen) to remove dissolved compounds via molecular bonding rather than physical capture. Chemical filtration is the third filter stage and removes molecules that mechanical + biological can't catch. Activated carbon (GAC): removes organic compounds (DOC), tannins, medications, odors. Replace every 3-4 weeks - exhausted carbon stops adsorbing. GFO (Granular Ferric Oxide): removes phosphate (PO4).
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