What Plants Need
Macronutrients: nitrogen, phosphorus, potassium.
Micronutrients: iron, magnesium, manganese, calcium, trace metals.
Light and CO2 (dissolved).
Low-Tech (No CO2) Tanks
Fish waste typically supplies enough nitrogen.
Dose Seachem Flourish Comprehensive weekly at 1/4 bottle recommendation.
Root tabs (API, Flourish Tabs) for heavy rooters like Amazon Swords.
High-Tech (CO2) Tanks
CO2 injection triples growth rate and nutrient demand.
EI (Estimative Index) method doses generously with water changes.
PPS-Pro and ADA step systems as alternatives.
Signs of Deficiency
Yellow leaves — nitrogen or iron.
Holes in leaves — potassium.
Slow growth — potassium or general nutrient.
Stunted top growth — trace elements.