What is Nitrate?
Nitrate (NO3-) is the final product of the nitrogen cycle - the result of beneficial bacteria processing ammonia through nitrite. Unlike its precursors, nitrate isn’t immediately toxic at typical aquarium levels, but it still needs management.
Think of nitrate as a slow poison rather than an acute one. Low levels are tolerable, but accumulation over time causes chronic stress, health problems, and can contribute to algae blooms.
Why Nitrate Is Different
While ammonia and nitrite must always be zero, nitrate has a more nuanced relationship with shrimp:
Tolerable But Not Ideal
- Shrimp can live with moderate nitrate levels (under 20 ppm)
- Higher levels (20-40 ppm) cause chronic stress
- Very high levels (40+ ppm) cause visible health problems
- Acute toxicity typically starts around 80-100 ppm
The Accumulation Problem
Nitrate doesn’t naturally leave your tank like ammonia and nitrite (which get converted). It just accumulates:
- Waste produces ammonia
- Bacteria convert ammonia to nitrite
- Bacteria convert nitrite to nitrate
- Nitrate builds up… and builds up… and builds up
The only ways nitrate leaves are:
- Water changes (physically removing it)
- Plant consumption (biological removal)
- Denitrification (advanced - deep substrate bacteria)
Ideal Nitrate Levels
| Level | Status |
|---|---|
| 0-5 ppm | Excellent |
| 5-10 ppm | Ideal |
| 10-20 ppm | Acceptable |
| 20-40 ppm | Elevated - increase water changes |
| 40+ ppm | High - action needed |
Most successful shrimp keepers aim to keep nitrate below 10 ppm through regular water changes and/or heavy planting.
Effects of High Nitrate
On Shrimp Health
- Reduced breeding activity
- Failed molts
- Color fading
- Weakened immune system
- Shortened lifespan
- Deaths in sensitive species (Caridina, Sulawesi)
On Tank Ecology
- Algae blooms (algae love nitrate)
- Plant health issues (ironically - too much can cause problems)
- General water quality decline
- Creates conditions for disease outbreaks
Old Tank Syndrome
A particularly dangerous situation develops in neglected tanks:
How It Happens
- Hobbyist stops doing regular water changes
- Nitrate slowly accumulates over months
- Existing shrimp gradually adapt to rising levels
- New shrimp added to tank die within days
- Owner is confused - “my other shrimp are fine!”
Why It’s Tricky
The adapted shrimp have slowly acclimated to conditions that are lethal for newcomers. Even the adapted shrimp are stressed, but their gradual adjustment masked the problem.
The Fix
Resume water changes, but gradually. Dropping nitrate from 100 ppm to 20 ppm in one water change can shock the adapted inhabitants. Lower nitrate by 10-15 ppm per water change over several weeks.
Nitrate Control Methods
Water Changes (Primary Method)
The simplest and most reliable approach:
- 10-20% weekly for typical tanks
- 25-30% weekly for heavily stocked tanks
- Less frequent for heavily planted tanks with low bioload
Match new water parameters (temperature, TDS, etc.) to tank water.
Live Plants (Highly Effective)
Plants consume nitrate as fertilizer. Best options:
Fast-Growing Stems:
- Hornwort
- Water Sprite
- Elodea/Anacharis
- Rotala species
Floating Plants:
- Salvinia
- Frogbit
- Red Root Floaters
- Water Lettuce (check legality in your area)
Emergent Plants:
- Pothos (extremely effective)
- Lucky Bamboo (leaves above water)
- Peace Lily
Pothos in particular is famous for nitrate absorption - a few stems with roots in your filter or hang-on-back can keep nitrates near zero.
Reduce Input
Less food = less waste = less nitrate:
- Feed only what shrimp consume in 2-3 hours
- Remove uneaten food
- Don’t overfeed “for biofilm” - established tanks have plenty
- Consider feeding every other day
Testing Tips
The API Nitrate Test is notorious for false readings:
Critical Step: Bottle #2 contains reagent that crystallizes. You MUST shake it vigorously for 30+ seconds, then shake the test tube vigorously for another full minute. Without this, you’ll get inaccurate (usually high) readings.
Test regularly to understand your tank’s nitrate accumulation rate. This helps you dial in the right water change schedule for your specific setup.
Nitrate by Species Family
Different shrimp families have evolved in different environments, leading to varying nitrate requirements. Understanding these differences is crucial for successful shrimp keeping.
| Family | Acceptable Range | Optimal Range | Example Species | Notes |
|---|---|---|---|---|
| Neocaridina | 0-20 ppm | 0-10 ppm | Cherry Shrimp | Hardy, tolerates wider ranges |
| Caridina | 0-20 ppm | 0-10 ppm | Crystal Red Shrimp | Sensitive, requires stable parameters |
| Sulawesi | 0-20 ppm | 0-10 ppm | Cardinal Shrimp | Unique requirements, warm alkaline water |
Sensitive, requires stable parameters
Unique requirements, warm alkaline water
Stability Over Perfection
While hitting optimal ranges is ideal, stability is more important than exact numbers. Consistent parameters within the acceptable range are better than fluctuating values that occasionally hit optimal.
How to Test Nitrate
Accurate testing is essential for maintaining proper nitrate levels. Here are the most common testing methods, each with their own trade-offs.
Liquid Test Kit
Pros
- Accurate ppm reading
- Important: SHAKE BOTTLE #2 VIGOROUSLY for 30+ seconds
- Color chart shows concentration levels
Cons
- Common user error from not shaking reagent
- Takes 5 minutes for accurate reading
- Orange/red colors can be hard to distinguish
Test Strips
Pros
- Quick results
- Multiple parameters at once
- Good for trend monitoring
Cons
- Less precise
- Color matching can be tricky
Quick Comparison
| Method | Accuracy | Cost | Best For |
|---|---|---|---|
| Liquid Test Kit | High | $ | Recommended choice |
| Test Strips | Medium | $ | General use |
Testing Tip
Test at the same time of day for consistent results. Water parameters can fluctuate based on feeding, lighting, and CO2 levels. Morning tests before lights-on often provide the most stable readings.
How to Adjust Nitrate
Sometimes you need to adjust your nitrate levels. Here are safe methods for both raising and lowering values. Always make changes gradually - sudden parameter swings can stress or kill shrimp.
How to Lower Nitrate
Decrease nitrate levels
Regular Water Changes
10-20% weekly water changes are the primary nitrate removal method. Consistent schedule is key.
Live Plants
Fast-growing plants like hornwort, water sprite, and floating plants consume nitrate as fertilizer
Pothos/Emergent Plants
Grow pothos or other emergent plants with roots in water - extremely effective nitrate sponges
Reduce Feeding
Less food = less waste = less nitrate production. Feed only what shrimp consume in 2 hours.
Increase Plant Mass
More plants = more nitrate consumption. Heavily planted tanks often have near-zero nitrates.
Warnings
- Never do massive water changes to quickly lower nitrate - parameter swings are dangerous
- Very low nitrates can lead to deficiencies in planted tanks - balance is key
- Nitrate absorbing resins exist but are less effective than plants/water changes
Critical Safety Notice
Never make sudden, large changes to water parameters. Shrimp are extremely sensitive to parameter swings. All adjustments should be made gradually over hours or days, not minutes. When in doubt, go slower. Test frequently during adjustments to monitor progress.
Nitrate FAQ
While shrimp can tolerate higher nitrate than ammonia/nitrite, levels above 40-60 ppm cause chronic stress. Aim to keep nitrate below 20 ppm, ideally below 10 ppm. Very high nitrate (80+ ppm) can cause molting problems, reduced breeding, and weakened immune systems.
The #1 mistake with API nitrate tests is not shaking Bottle #2 vigorously. The reagent settles and crystallizes - you MUST shake it hard for at least 30 seconds, then shake the test tube for another minute. Without proper shaking, you'll get false high readings.
Old tank syndrome occurs when nitrate gradually accumulates over months/years in tanks with infrequent water changes. Existing inhabitants slowly adapt, but new additions die from nitrate shock. The solution is resuming regular water changes, but gradually - a massive sudden water change can shock adapted inhabitants.
Zero nitrate is possible in heavily planted tanks where plants consume all available nitrate. For shrimp-only setups, this is fine. For planted tanks, you might need to dose small amounts of nitrate as fertilizer. Zero nitrate in an unplanted tank suggests the test or cycle might not be working correctly.
Absolutely. Fast-growing plants are essentially biological nitrate filters. Tanks with heavy plant loads often maintain near-zero nitrates between water changes. Floating plants and emergent plants (pothos, lucky bamboo) are especially effective because they have unlimited CO2 access.
Standard recommendation is 10-20% weekly for most setups. Test your tank to find your nitrate accumulation rate, then adjust accordingly. Heavily stocked tanks may need more frequent changes; heavily planted tanks may need less. Consistency matters more than volume.
Track Your Nitrate with ShrimpKeeper
Stop guessing. Start tracking. ShrimpKeeper gives you species-specific nitrate ranges, instant diagnostics, and historical graphs for your colony.
Nitrate Problems & Troubleshooting
Bacterial Infection in Shrimp
HighIdentifying and treating bacterial infections in aquarium shrimp. Learn to recognize symptoms and understand why prevention through water quality is more effective than treatment.
Why Won't My Shrimp Breed?
MediumTroubleshooting guide for shrimp colonies that aren't producing berried females or offspring. Learn the key factors that trigger and sustain breeding.
Vorticella (White Fuzz) on Shrimp
MediumUnderstanding and treating vorticella - the white fuzzy growth that appears on shrimp shells. Learn why it happens and effective treatment options.