What's a healthy nitrate level?
Nitrate (NO₃) is the end product of your tank's biological filtration — fish waste and leftover food break down into ammonia, then nitrite, then nitrate. A little is normal and even useful; corals use it. Too much is the problem.
| Tank type | Target nitrate |
|---|---|
| Mixed reef / LPS | 2–10 ppm |
| SPS-dominant | 1–5 ppm |
| Fish-only / soft coral | up to ~20 ppm is tolerable |
Chasing zero is a mistake — bottomed-out nitrate starves corals and can trigger its own problems. Aim for low and stable, not zero.
What makes nitrate climb
- Overfeeding and too many fish for the system's size
- Detritus building up in the sump, rock, and low-flow corners
- A skimmer that's undersized or poorly tuned
- Infrequent or too-small water changes
- Clogged filter socks or pads left in too long
7 ways to lower nitrates
- Water changes. The simplest lever. A 10–20% change with quality salt mix directly removes nitrate. Consistency beats size — a steady weekly rhythm outperforms a big change once a month.
- Feed less, feed smarter. Feed what's eaten in a couple of minutes. Soak dry food to rinse off phosphate, and target-feed corals instead of dumping into the water column.
- Dial in your skimmer. A properly sized, well-tuned protein skimmer pulls organics out before they mineralize into nitrate. Clean the cup and neck regularly.
- Export with a refugium. Chaetomorpha or other macroalgae under a grow light consumes nitrate and phosphate. Harvest it as it grows — that's the export.
- Carbon dosing. Vodka, vinegar, or a commercial carbon source feeds bacteria that consume nitrate. Powerful, but go slow and test often — overdosing swings parameters fast.
- Nitrate-reducing media. Biopellets or a dedicated denitrator give anaerobic bacteria a home to process nitrate. Pair with good flow through the reactor.
- Clean up detritus. Blow off the rock with a turkey baster, rinse filter socks often, and vacuum the sump. You can't export what's still trapped in the tank.
Bring it down slowly
Corals adapt to stability, not swings. If nitrate is high, don't crash it to near-zero in a day — a fast drop can bleach or shock livestock as badly as the high reading did. Move it a few ppm at a time and let the tank settle.
Track it so it doesn't creep back
Most nitrate problems are slow creeps you don't notice until algae shows up. Log every test so you can see the trend line, not just today's number — that's exactly what TankMate does: log your nitrate in seconds, watch the trend, and get an AI read on what your combined parameters mean for your corals. It's free on Google Play.