FishTankWater test results: what do my numbers mean?
Type in your aquarium test results and this free tool tells you, line by line, whether each number is safe, what it means for your fish, and what to do next. It also works out how toxic your ammonia really is at your pH and temperature.
Test results (leave blank if you didn't test it)
Strips and liquid kits both read in steps (0, 0.25, 0.5, 1 ppm and so on), so pick the nearest color. If a reading looks wrong, test again with a fresh sample.
Keep a record of your tank. Get my free printable tank log: 13 weeks of water tests, water changes and filter care, with healthy levels at a glance.
Send me the free logSafe levels at a glance
| Test | Good | Watch | Act now |
|---|---|---|---|
| Ammonia | 0 ppm | 0.25 ppm | 0.5 ppm or more |
| Nitrite | 0 ppm | 0.25 ppm | 0.5 ppm or more |
| Nitrate | Under 20 ppm | 20–40 ppm | Over 40 ppm |
| pH | 6.5–7.8 and steady | 6.0–6.5 or 7.8–8.4 | Under 6.0, over 8.4, or swinging |
| KH (carbonate hardness) | 3–8 dKH | 2–3 dKH | Under 2 dKH (pH can crash) |
| GH (general hardness) | 4–12 dGH | 3–4 or 12–18 dGH | Under 3 dGH (snail and shrimp shells suffer) |
| Temperature (tropical) | 74–80°F | 72–74 or 80–84°F | Under 72°F or over 84°F |
Why the same ammonia reading can be safe or deadly
Test kits measure total ammonia. Only part of it is the toxic form, free ammonia (NH3), and that part grows fast as pH and temperature rise. At pH 6.8, 1 ppm of total ammonia is fairly mild. At pH 8.2, the same 1 ppm is about 25 times more toxic. That's why this tool asks for your pH and temperature: it shows the NH3 number too. Fish start to suffer above about 0.02 ppm NH3, and it gets dangerous above 0.05 ppm.
Even so, any ammonia or nitrite in a tank with fish means the filter can't keep up. Do a water change and find out why: a new tank, too many fish, too much food, a dead fish or a filter that was cleaned too hard. See ammonia in a fish tank and nitrite in a fish tank.
Reading a cycling tank
In a new tank with no fish, ammonia and nitrite are a good sign: the bacteria are growing. Keep ammonia at about 2 ppm, and if nitrite climbs over about 5 ppm, do a big water change so the cycle doesn't stall. The tank is cycled when it turns 2 ppm of ammonia into 0 ammonia and 0 nitrite within 24 hours, with nitrate showing up. See how to cycle a fish tank.
Testing and emergency picks
Paid links: if you buy through these Amazon links, I earn a small commission at no extra cost to you.
- Test kitAPI Freshwater Master Test KitMore accurate than strips, and it lasts for hundreds of tests.
- Test stripsTetra EasyStrips 6-in-1 (100 strips)Quick weekly checks, including KH and GH.
- Water conditionerSeachem Prime (500 ml)Binds ammonia and nitrite for 24–48 hours while you do water changes.
- Water changerPython No Spill Clean and Fill, 25 ftMakes big emergency water changes a lot faster.
Related: Fish symptom checker · Water change calculator · Dosing calculator · Best aquarium test kits · Aquarium pH