When a new tank is set up, ammonia from waste must be turned into nitrite and then nitrate before the water is safe. Does adding live plants change how fast a tank reaches that stable state?
A jar with live plants will reach lower peak ammonia and nitrite, and arrive at stable nitrate sooner, than an identical jar with no plants.
Live plants present in one jar, absent in the other.
Ammonia, nitrite, and nitrate, in mg per liter, over time.
Water volume, temperature, light, ammonia dose, and jar type.
- Identical glass jars 2, about 4 L each
- Dechlorinated water 4 L per jar, 8 L total
- Egeria densa, fast growing stem plant 6 stems, about 15 cm, jar A only
- Pure ammonia solution, no scent or detergent dose to 2 mg per liter
- Freshwater test kit, ammonia, nitrite, nitrate 1 kit
- Aquarium thermometer 1
- LED lamp on a timer about 800 lumens, 8 hr per day
- Logbook or spreadsheet 1
- Label the jars A and B. Fill each with exactly 4 L of dechlorinated water.
- Place the 6 plant stems in jar A only. Leave jar B as water alone.
- Set both jars under the same lamp, 20 to 25 cm away, on a timer for 8 hours a day.
- Add pure ammonia to each jar until both read 2 mg per liter. Stir gently.
- Once a day at the same hour, measure ammonia, nitrite, and nitrate in each jar. Record every value and the temperature.
- Whenever ammonia reads 0, dose it back to 2 mg per liter to keep feeding the bacteria.
- Run for 6 weeks, or until a jar converts 2 mg per liter of ammonia to 0 nitrite within 24 hours.
| Day | Temp °C | NH₃ A | NH₃ B | NO₂ A | NO₂ B | NO₃ A | NO₃ B |
|---|---|---|---|---|---|---|---|
| 1 | |||||||
| 2 | |||||||
| 3 |
A is the planted jar, B is the unplanted jar. Record every day for the full run. The shape of these curves is your result.
Ammonia is converted to nitrite and then nitrate by nitrifying microbes, including comammox Nitrospira, which can perform both steps inside one cell. Plants change the picture: their roots and leaves take up ammonium and nitrate directly as fertilizer, and they release oxygen that aerobic nitrifiers depend on. So a planted jar has two routes removing nitrogen at once, microbial and botanical, which can lower the toxic peaks and reach a stable state faster.
If jar A shows lower peak ammonia and nitrite and reaches steady nitrate before jar B, the hypothesis is supported. If the two jars track together, it is not. One jar per group cannot rule out chance, so the honest next step is to repeat the experiment with several jars in each group and compare the averages. That is how a single observation becomes evidence.
