There are two ways to know what your plants need: read the plants (deficiency symptoms) or use test kits (nitrate, phosphate, iron). For most low-tech tanks, watching the plants is enough; high-tech and EI tanks benefit from testing. Here's how to do both.
Method 1 - read the plants (free)
Deficiency symptoms tell you a lot: pale new leaves point to iron, yellowing older leaves to nitrogen, pinholes and yellow edges to potassium, and stunted tips to calcium or micros. Our deficiency guide matches each symptom to a nutrient, so you top up the right thing - Potassium or Iron - instead of guessing.
Method 2 - test kits
Liquid test kits for nitrate (NO3), phosphate (PO4) and iron (Fe), plus GH/KH, let you measure nutrient levels directly - useful if you run CO2 and dose heavily. Keep levels in a healthy range and adjust dosing to match uptake (see our EI dosing and dosing guides).
Which should you use?
- Low-tech / budget: observation plus a steady all-in-one (Sunken Garden Green) is plenty.
- High-tech / EI: add test kits to fine-tune and avoid excess, which feeds algae (see fertiliser & algae).
Frequently asked questions
How do I know what fertilizer my aquarium plants need?
Read deficiency symptoms on the plants, or use test kits for nitrate, phosphate and iron - observation suffices for most low-tech tanks.
Do I need test kits for a planted tank?
Not for low-tech tanks - watching the plants is enough. Test kits help high-tech, heavily dosed tanks.
Which test kits are useful for plants?
Nitrate (NO3), phosphate (PO4) and iron (Fe), plus GH/KH for water hardness.
How do I read plant deficiency symptoms?
Pale new leaves suggest iron; yellow old leaves nitrogen; pinholes potassium - match the symptom to a deficiency guide.
Can I fertilize without testing?
Yes - a consistent all-in-one plus observation works for most tanks; testing just adds precision.
What if tests show high nutrients?
Ease off dosing and do a water change - excess nutrients can feed algae if plants aren't using them.
Dose what your plants actually need with targeted supplements from Fish Bazaar - Potassium, Iron and Sunken Garden all-in-one, delivered across India.
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