Signs of nutrient deficiency in aquarium plants
Where a symptom appears tells you a lot. Mobile nutrients (N, P, K, Mg) are pulled from old leaves first; immobile ones (iron and most traces) show up in new growth.
| Nutrient | Where first | What you see |
|---|---|---|
| Nitrogen | Older leaves | Overall pale or yellow leaves, stunted growth, red plants turning very red but small |
| Phosphorus | Older leaves | Stunted growth, unusually dark green leaves, green spot algae on glass and slow leaves |
| Potassium | Older leaves | Pinholes, yellow or brown edges, weak stems (very common in fast stem plants) |
| Magnesium | Older leaves | Yellowing between veins while veins stay green |
| Iron | New leaves | New growth pale yellow to white with green veins; thin, short stems |
| Calcium / boron | Growing tips | Twisted or stunted new leaves, dying tips |
Before you blame fertilizer
- CO₂ and light limit growth more often than nutrients in high-tech tanks.
- Melting after planting is normal for many plants.
- Change one thing at a time and wait a week or two; new leaves show the result.
Fixing it
Raise the suspected nutrient by 25–50 % for a couple of weeks. For potassium, the calculator's K₂SO₄ top-up is the cleanest fix because it adds no N or P. Iron problems usually respond to more trace mix or a dedicated iron product; keep an eye on copper if you keep shrimp. Start from lean EI and raise single targets.
Where to buy · Retailer links coming soon.
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Sources
- Seachem Flourish Nitrogen: deficiency signs
- Seachem Flourish Phosphorus: deficiency signs
- Seachem Flourish Potassium: deficiency signs in older leaves
- Seachem Flourish Iron: deficiency signs in new growth
Written in our own words from the sources above. Numbers are educational starting points; check product labels and your water.