Nitrite (Nitrite (NO2-))

What is Nitrite?

Nitrite (NO2-) is the second compound in the nitrogen cycle, produced when beneficial bacteria (Nitrosomonas) convert ammonia. It’s an intermediate product that gets further converted to nitrate by a second group of bacteria (Nitrobacter).

Like ammonia, nitrite has no safe level for shrimp - it must always be 0 ppm in an established tank. Any detectable nitrite indicates either an incomplete cycle or a cycle crash.

The Mid-Cycle Danger

During tank cycling, nitrite often becomes the bigger problem after ammonia is under control:

The Typical Cycling Pattern

Week 1-2: Ammonia rises, no nitrite Week 2-4: Ammonia-eating bacteria establish, ammonia drops, nitrite SPIKES Week 4-6: Nitrite-eating bacteria establish, nitrite drops, nitrate rises Week 6+: Cycle complete - both ammonia and nitrite at 0

The nitrite spike phase is often when impatient new hobbyists add shrimp, thinking “ammonia is zero, it must be safe.” This is a critical mistake - the nitrite spike can be more dangerous than the initial ammonia phase.

How Nitrite Kills

Nitrite is toxic through a specific mechanism: it binds to hemocyanin, the oxygen-carrying protein in shrimp blood (analogous to hemoglobin in humans). When nitrite binds to hemocyanin:

1. The hemocyanin can no longer carry oxygen effectively
2. Shrimp begin to suffocate at the cellular level
3. Blood color changes from normal blue-green to brown
4. This condition is called “brown blood disease”

The cruel irony is that shrimp can be gasping in water saturated with oxygen - the oxygen is there, but their blood can’t transport it. Adding more aeration doesn’t help once nitrite toxicity sets in.

Sensitivity Comparison

Invertebrates like shrimp are generally MORE sensitive to nitrite than fish. While some hardy fish can tolerate brief nitrite exposure, shrimp have very little tolerance. Levels that would merely stress a fish can kill shrimp quickly.

Signs of Nitrite Poisoning

Early Signs

• Lethargy and reduced activity
• Loss of appetite
• Staying near water surface or filter output (seeking oxygen)
• Pale coloration

Advanced Signs

• Erratic swimming
• Lying on side
• Visible color change (brownish tint)
• Mass die-offs

Once advanced symptoms appear, it’s often too late to save affected shrimp.

Emergency Response

If you detect nitrite with shrimp in the tank:

Immediate Actions

1. 50%+ water change - Dilute nitrite immediately
2. Dose Seachem Prime - Detoxifies nitrite for 24-48 hours
3. Maximize aeration - Help struggling shrimp access what oxygen they can
4. Stop feeding - Reduce waste production

Continued Treatment

• Test nitrite twice daily
• Water change whenever Prime wears off
• Continue until nitrite stays at 0 for several days
• Add beneficial bacteria to speed recovery

If Possible

• Move shrimp to a fully cycled tank
• A temporary holding container with cycled filter media is better than nitrite exposure

Why Nitrite Spikes Happen

During Initial Cycling

This is normal and expected. Simply wait without adding livestock until both ammonia and nitrite process to 0 within 24 hours.

In Established Tanks

Filter Issues:

• Cleaning filter media with chlorinated tap water (kills bacteria!)
• Filter mechanical failure (no oxygen flow to bacteria)
• Replacing all filter media at once (removes bacteria colony)

Environmental Shocks:

• Major pH swing (bacteria are pH sensitive)
• Temperature spike or crash
• Medication use (antibiotics kill beneficial bacteria)
• Sudden salinity change

Overload:

• Major die-off (dead animals producing ammonia faster than bacteria can process)
• Severe overfeeding
• Sudden large increase in bioload

Cycling Patience

The #1 protection against nitrite problems is proper cycling BEFORE adding shrimp:

Minimum: 4-6 weeks with ammonia source Better: 6-8 weeks Best: 2-3 months (allows biofilm development too)

Test to confirm: The tank is cycled when 2 ppm ammonia converts to 0 ammonia + 0 nitrite within 24 hours, multiple times. Nitrate should be present (showing the full cycle is working).

No shortcut is worth dead shrimp. Let the bacteria establish fully before adding your colony.