What a complete feed looks like
Hydro formulas
Balanced mineral mixes meant to supply the full menu in soilless or hydro systems
Basic NPK bags
Many non-hydro fertilizers list only nitrogen, phosphorus and potassium and skip traces
Organics
Fish emulsion, guanos, manures and blended organics often carry extra micronutrients from the source material
Read the label
Incomplete menus are common. Check for calcium, magnesium and sulfur as well as NPK
Soilless need
Unenriched mixes need micronutrients plus calcium and magnesium. Rich soil in a large pot may need little extra
Stage demand
Vegetative nitrogen
Plants use more nitrogen before flower than later
Flower phosphorus
Phosphorus use rises when flowering starts
Flower potassium
Potassium demand climbs after pollination as flowers and seed form
Always some nitrogen
Even in bloom the plant still needs a little nitrogen to build amino acids and use P and K
Adjust nitrogen for climate and light
Hot rooms
Cut nitrogen 10 to 20 percent so extra transpiration does not concentrate salts and thin the stalk
Cool rooms
Raise nitrogen 10 to 20 percent because plants drink less water and take up less N
Strong light
Increase nitrogen under intense lamps
Weak light
Decrease nitrogen when light is modest
Mixing and medium notes
Stay in one line: Mixing brands can create mineral clashes. Use proven products and follow that company's chart.
Dolomite: Calcium magnesium carbonate is a simple soil buffer and Ca/Mg source.
Time-release: Some indoor fertilizers are mixed into the medium once rather than fed every watering.
Hydro organics: Most organics ferment in reservoirs and clog emitters, so they stay in soil systems.