How Do I Lower Nitrates in My Reef Tank?

High nitrates are one of the most common reef tank problems, but they're solvable. Most reef tanks should maintain nitrates between 5-10 ppm. SPS-dominant tanks often target under 5 ppm, while fish-only or soft coral tanks can tolerate up to 20 ppm.

Quick Fixes for High Nitrates

1. Water changes — The fastest solution. A 25% water change immediately reduces nitrates by 25%
2. Reduce feeding — Feed less frequently or smaller portions. Uneaten food decays into nitrates
3. Remove detritus — Vacuum the sandbed and clean filter socks more often
4. Check your source water — Some tap water contains nitrates. Use RO/DI water

Long-Term Nitrate Reduction Methods

Refugium with Macroalgae

A refugium filled with chaetomorpha or caulerpa absorbs nitrates as the algae grows. Harvest regularly to export the nutrients from your system. This is one of the most natural and effective methods.

Carbon Dosing

Adding carbon sources (vodka, vinegar, or commercial products like NoPox) feeds beneficial bacteria that consume nitrates. Start slowly—overdosing can crash oxygen levels. Best used with a good protein skimmer.

Biopellets

Similar to carbon dosing but more controlled. Biopellets provide a carbon source in a reactor, promoting bacterial growth that exports nitrates through your skimmer.

Clean Up Crew

Add snails, hermit crabs, and other invertebrates to consume detritus before it breaks down into nitrates.

Track Your Progress

Test nitrates weekly and log results in the ReefBay app to track trends. Sudden spikes often indicate a dying fish, overfeeding, or filter maintenance issues.

What NOT to Do

• Don't do massive water changes (over 50%) — this stresses livestock
• Don't add chemical nitrate removers without understanding how they work
• Don't panic at slightly elevated levels — stable nitrates are better than fluctuating ones

Patience is key. Most nitrate reduction methods take 2-4 weeks to show significant results.