| What They Are | Accumulated dissolved nutrients |
| Nitrate Target | Roughly 5–10 ppm (not zero) |
| Phosphate Target | ~0.03–0.1 ppm |
| Main Symptom | Algae, cyano, dull corals |
| Best Fixes | Export: skimming, water changes, media |
Overview
Nitrate and phosphate are the end products of feeding and fish waste. A little of each is normal and even necessary — corals need some nutrients — but when they climb, you get nuisance algae, cyanobacteria, and browned-out corals. Lowering them is about export: physically removing nutrients faster than they accumulate. Note the targets are low, not zero; bottoming them out invites dinoflagellates.
How to Lower Them
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- Water changes — the simplest export: fresh saltwater dilutes both. Regular, consistent changes prevent buildup in the first place.
- Protein skimming — a good skimmer pulls organics out before they break down into nitrate and phosphate.
- Feed less, and better — overfeeding is the number-one source; feed what fish eat in a minute or two and remove excess.
- Phosphate media (GFO) — granular ferric oxide in a reactor pulls phosphate down directly.
- Carbon dosing / refugium — vodka/vinegar dosing or a chaeto refugium grows something that consumes nitrate and phosphate, which you then export.
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Do It Gradually
Bring nutrients down slowly. Corals acclimated to high nutrients can bleach if you strip the water too fast, and crashing phosphate overnight is a classic trigger for dinos and cyano. Aim to reduce over weeks, not hours, and let corals adjust.
Common Mistakes
Aiming for zero: ultra-low-nutrient tanks look great until they crash into dinos — keep a little nitrate and phosphate. Only adding media without cutting feeding: you’re bailing while the tap runs. Ignoring source water: tap or exhausted RODI adds the very phosphate you’re fighting — see our RODI guide.
Related Guides
How to Beat Hair Algae (Green Hair Algae) · How to Get Rid of Red Slime (Cyanobacteria) · Emerald Crab