Ammonia & Nitrate Levels for Betta Fish
Short answer: Zero ammonia and 5 ppm nitrate. Across 119 betta tanks scraped from r/bettafish, the median ammonia is 0 ppm and the median nitrate is 5 ppm. 92% of tanks keep nitrate at 20 ppm or below.
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Stocking — under 85% comfortable · 85–100% full · over 100% overstocked
Show the math
Zero ammonia and 5 ppm nitrate. Those are the medians across 119 ammonia readings and 118 nitrate readings scraped 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) | 119 | 0.0 | 1.0 | 0-0 | 0-30 |
| Nitrate (ppm) | 118 | 5.0 | 9.1 | 0-10 | 0-100 |
75% of betta tanks read exactly 0 ppm ammonia (the IQR is 0-0). The mean is higher (1.0 ppm) because a few tanks with active problems pull it up, including one extreme outlier at 30 ppm. For nitrate, 92% of tanks stay at 20 ppm or below, and only 2.5% exceed 40 ppm.
Why ammonia must be zero
Ammonia is the first waste product fish produce, and it is directly toxic. 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. 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. 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
We scraped 2,192 tank posts from fishkeeping subreddits (primarily r/bettafish) where keepers shared water test results. Of those, 119 betta posts included an ammonia reading and 118 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/.
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
Gear for this setup
As an Amazon Associate AquaGauge earns from qualifying purchases. Some links below are affiliate links, at no extra cost to you. Current price and availability are shown on Amazon. Disclosure.
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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 119 betta tanks, the median ammonia is 0.0 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 118 betta tanks is 5 ppm, and 92% 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.