neon tetra fish in aquarium

Aquarium plant health guide

Mineral deficiencies can be detected by observing the plants and their symptoms.

Magnesium, nitrogen, phosphate, potassium for example are mobile nutrients and calcium, iron are immobile.

Mobile nutrients can be moved within the plant to avoid a shortage while a deficiency in immobile nutrients has an instant effect on the plant.

Signs of plant deficiencies:

Old leaves turn yellowish/ redNitrogen deficiency
Old leaves turn yellowish/ red; Leaf loss and small dead areasPhosphate deficiency
Black/ brown leaves, plants dieExcess phosphates
Yellow spots on old leaves and yellowish margins on younger leavesPotassium deficiency
Yellowish margins on young leaves with deformationsCalcium deficiency
Yellow spots on old leaves while veins stay greenMagnesium deficiency
Young leaves turn yellowSulfur deficiency
Yellowing leaves starting from the tip then become transparentIron deficiency
Yellow spots between the veins, margins and tipsZinc deficiency
Plant stays small slow or now growth white deposits on leaves (calcium)CO2 deficiency
Fish gasp for air on surfaceExcess CO2
Sluggish fish no plant growthOxygen deficiency
Plants stop growing/ black rootsSubstrate problem

Additional considerations:

Carbon Dioxide (CO2)

A possible source for a CO2 deficiency can be a well aerated tank. Airstones or high surface turbidity can diffuse the CO2.

Excess CO2 can be a result of poor lighting (the better the lighting the easier, the CO2 uptake of the plants), or an over fertilization of CO2.

Substrate Problems

The substrate is either to loose or compacted. If agitated gas bubbles can be detected on the the surface. This is also an indication that the substrate is old and in need of replacement.

Water Temperature

Plants will stop growing and die off if the water is to cold. Higher temperatures will result in smaller leaves and larger gaps between these leaves.


Light is essential for photosynthesis. Not enough wattage or aging bulbs will stun the plant growth. Plants look weak with small pale green leaves. Plants closer to the light will be less effected.

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