Ammonia & Nitrate Levels for Betta Fish
Short answer: Zero ammonia and 5 ppm nitrate. Across 194 betta tanks compiled from r/bettafish, the median ammonia is 0 ppm and the median nitrate is 5 ppm. 93% of tanks keep nitrate at 20 ppm or below.
Betta at a glance
- Scientific name
- Betta splendens
- Adult size
- ~2.5″
- Temperature
- 76–82°F
- pH
- 6.5–7.5
- Minimum tank
- 5 gal
- Temperament
- aggressive
- Social
- can be kept singly
- Reference
- Wikipedia
Zero ammonia and 5 ppm nitrate. Those are the medians across 125 ammonia readings and 123 nitrate readings in the AquaGauge dataset (July 2026 snapshot), drawn from r/bettafish posts where keepers shared water test results. If your betta tank matches those numbers, your water quality is normal.
What real betta keepers actually measure
| Parameter | N (tanks) | Median | Mean | IQR | Full range |
|---|---|---|---|---|---|
| Ammonia (ppm) | 125 | 0 | 1.1 | 0-0 | 0-30 |
| Nitrate (ppm) | 123 | 5 | 9 | 0-10 | 0-100 |
75% of betta tanks read exactly 0 ppm ammonia (the IQR is 0-0). The mean is higher (1.1 ppm) because a few tanks with active problems pull it up, including an extreme outlier at 30 ppm. For nitrate, 93% of tanks stay at 20 ppm or below, and only 2% exceed 40 ppm.
Why ammonia must be zero
Ammonia is the first waste product fish produce, and it is directly toxic. For a broader look at safe ammonia levels across all freshwater tanks: across 902 tanks that reported ammonia, the median is 0 ppm and only 31% show any detectable reading. Even 0.25 ppm burns gill tissue and suppresses the immune system. At 1 ppm, damage is visible within hours: clamped fins, gasping at the surface, red streaks on the body.
A working nitrogen cycle converts ammonia to nitrite and then to nitrate. In a cycled tank, ammonia stays at 0. Any detectable reading means something broke: the filter stalled, you cleaned the media in tap water, you overfed, or the tank was never cycled in the first place.
If ammonia reads above zero, do a 50% water change immediately. Then find and fix the cause. A water change schedule keeps things on track.
Nitrate: under 20 ppm is the real-world benchmark
Nitrate is the end product of the nitrogen cycle and is much less toxic than ammonia, but it still matters at high concentrations.2 Above 40 ppm, long-term exposure leads to stunted growth and weakened immunity. Above 80 ppm, acute toxicity is possible.
Real betta keepers land well below those danger zones. The median is 5 ppm and the IQR is 0-10 ppm, which means 75% of tanks sit at 10 ppm or under. Weekly water changes of 20-30% in a properly sized betta tank are enough to keep nitrate low.
Live plants help too. Planted tanks pull nitrate out of the water column as fertilizer, which is one reason many keepers in our dataset report 0 ppm nitrate.
Ammonia vs nitrate: which matters more?
Ammonia, by far. A betta at pH 7.4 with 0 ammonia and 15 ppm nitrate is fine.1 A betta at the same pH with 0.5 ppm ammonia and 0 nitrate is in trouble. Ammonia is acutely toxic; nitrate is a slow accumulator.
Test ammonia first. If it is 0, test nitrate. If nitrate is under 20, your water is clean. That is the priority order.
How we counted
The AquaGauge dataset covers 6,414 real tanks compiled from 12 aquarium subreddits. Of those, 194 tanks from r/bettafish reported at least one water test result: 125 included an ammonia reading and 123 included a nitrate reading. All numbers on this page come from those readings, verified by verify_stats.py. See examples: source 1, source 2. Full methodology at /methodology/. Figures are from the July 2026 snapshot (6,414 tanks total).
Check your exact stocking
Add your fish below to see stocking %, filtration load and compatibility for your setup — live.
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Stocking — under 85% comfortable · 85–100% full · over 100% overstocked
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Gear for this setup
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API Freshwater Master Test Kit Liquid reagent tests for ammonia, nitrite, nitrate, and pH in one box. More accurate than strips, and the ammonia test catches readings below 0.25 ppm. Check price on Amazon →
FAQ
- What ammonia level is safe for a betta?
- Zero. Across 125 betta tanks in the AquaGauge dataset that reported ammonia, the median is 0 ppm and 75% of tanks read exactly 0. Any detectable ammonia means the tank is not fully cycled or is overstocked.
- What nitrate level is safe for a betta?
- Under 20 ppm. The median across 123 betta tanks is 5 ppm, and 93% of keepers stay at 20 ppm or below. Above 40 ppm, do a water change.
- How do I lower ammonia in a betta tank?
- Water change first (50% immediately if ammonia is above 0.25 ppm), then fix the cause: cycle the filter, reduce feeding, or remove uneaten food. Detoxifiers like Prime buy time but do not replace a working nitrogen cycle.
- How often should I test betta water for ammonia and nitrate?
- Weekly with a liquid test kit. Test more often during cycling (daily) or after adding new stock. Strips are less accurate for ammonia.
Sources
- Betta splendens, Seriously Fish. View source ↗
- Betta splendens summary, FishBase. View source ↗
Freshwater aquarist of 8+ years.