mg/L
Iron
What is it
Iron (Fe) is a trace nutrient plants need for chlorophyll formation and new growth. In aquariums it is usually supplied through comprehensive trace fertilizers.
Why it matters
Fast stems and red plants show iron or trace shortages quickly in pale new tips. Iron also becomes unavailable more easily at high pH or when dosing is inconsistent.
Interactions with other parameters
Iron availability is affected by pH, chelator type, light intensity and plant growth speed. It works with nitrate, phosphate and CO2 rather than replacing them.
Ideal ranges
| Tank type | Min | Max | Unit |
|---|---|---|---|
| Tropical community | 0.05 | 0.2 | mg/L |
| Planted high-tech | 0.2 | 0.5 | mg/L |
| Planted low-tech | 0.05 | 0.1 | mg/L |
| Shrimp tank | 0.01 | 0.05 | mg/L |
Out of range: what happens
Low available iron can cause yellow new leaves, weak color and stalled shoot tips. Excess trace dosing can irritate sensitive animals and may contribute to algae if the tank is already imbalanced.
Common Myths
- •Red plants only need lots of iron; light, CO2 and overall nutrition matter just as much.
- •A zero iron test always means none is available; the kit may not detect the chelated form.
How to measure
Iron test kits only show part of the picture because chelated iron may not read cleanly. Use them as a trend tool, then confirm with plant response.
How to adjust
Dose a complete trace fertilizer in small regular amounts. Improve CO2 and macro balance before chasing high iron numbers.
Pro Tips
Dose traces after water changes or in smaller daily portions for steadier availability.
Watch the newest leaves first: they reveal iron and trace issues sooner than old leaves.
