Nitrate creep is the #1 silent killer in established tanks. Above 30 ppm in freshwater, above 25 ppm in reef, you start seeing algae blooms, coral bleaching, and immune-stressed fish. Here's the protocol-driven cleanup.
Before fixing nitrates, identify what's driving them. Common culprits: overfeeding (most common), overstocked tank, insufficient filtration, uneaten food in substrate, dead zone in rockwork, tap water with elevated nitrate (test your tap with the same kit).
The brute-force fix. 25-30% weekly minimum during cleanup. For nitrate above 50 ppm in reef tank, consider 30% twice weekly until you hit target. Use RO/DI water for reef, conditioned tap for freshwater.
Reef: Brightwell NeoNitro, Red Sea NO3-PO4-X, or carbon dosing (vinegar / vodka). Each works by stimulating bacteria that consume nitrate. Freshwater: Seachem Purigen for short-term, plus Pothos plants growing emersed (hugely effective).
Macroalgae refugium (reef tanks): chaeto in a sump compartment with a refugium light. Consumes nitrate + phosphate continuously.
Heavily planted tank (freshwater): live plants outcompete algae and consume nitrogen. Pothos / philodendron rooted in HOB filter is the cheapest hack.
Reduce feeding. Most hobbyists overfeed by 2-3x. Aim: fish should fully consume food in 60-90 seconds, no leftovers settling on substrate.
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Browse test kits →Reef: 2-15 ppm. SPS-dominant: under 10 ppm. Freshwater community: under 30 ppm. Discus + sensitive species: under 10 ppm. Above 40 ppm in reef = visible coral stress within 30 days.
Don't drop more than 50% per week. Sudden parameter swings stress fish more than the elevated nitrate. From 80 ppm: target 40 ppm by week 1, 20 ppm by week 2, 10 ppm by week 3.
Recommendations on this page cross-checked against the following authoritative references and our internal vendor + breeder database.