Nitrate (NO3) is the end product of the nitrogen cycle - bacteria don't process it further in normal aquariums. Freshwater methods: 1) Larger water changes (50% weekly drops nitrate proportionally - the math is exact). 2) Live plants - stem plants (rotala, ludwigia, hornwort) and floaters (frogbit, water lettuce) consume nitrate as fertilizer. 3) Reduce feeding. 4) Reduce stocking. 5) Pothos plant rooted in tank water (cheap nitrate sponge). Saltwater methods: 1) Refugium with chaetomorpha (chaeto) - lit 24/7 or reverse photoperiod, exports phosphate too. 2) Carbon dosing (vodka, vinegar, NoPoX, Red Sea NO3:PO4-X) - feeds bacteria that out-compete algae for nitrate. Risky if dosed without skimmer running 24/7. 3) Biopellets - solid carbon source in fluidized reactor. 4) Nitrate reactor - anaerobic chamber that converts NO3 to N2 gas. 5) Algae turf scrubber. Targets: freshwater = under 30 ppm. Reef = under 5 ppm for SPS, under 10 ppm for mixed reef. Test first: Salifert + Red Sea + Hanna nitrate kits - cheap strips lie about nitrate.
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