Aquarium plant health guide

neon tetra fish in aquarium

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.

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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:

Symptoms Cause
Old leaves turn yellowish/ red Nitrogen deficiency
Old leaves turn yellowish/ red; Leaf loss and small dead areas Phosphate deficiency
Black/ brown leaves, plants die Excess phosphates
Yellow spots on old leaves and yellowish margins on younger leaves Potassium deficiency
Yellowish margins on young leaves with deformations Calcium deficiency
Yellow spots on old leaves while veins stay green Magnesium deficiency
Young leaves turn yellow Sulfur deficiency
Yellowing leaves starting from the tip then become transparent Iron deficiency
Yellow spots between the veins, margins and tips Zinc deficiency
Plant stays small slow or now growth white deposits on leaves (calcium) CO2 deficiency
Fish gasp for air on surface Excess CO2
Sluggish fish no plant growth Oxygen deficiency
Plants stop growing/ black roots Substrate 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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6 thoughts on “Aquarium plant health guide

  1. Doug says:

    Site looks great! Mobile works well. My plants are having the base dye and the plants keep floating up. I tested the water and it’s acidic. How do I add base? Hardness is high because I use well water since my tap is softened. I figured the iron in the water wouldn’t hurt. Should I go back to buying spring water?

    • Thilo @ Algone
      Thilo @ Algone says:

      You can increase the pH level by adding baking soda (1 teaspoon per 10 Gallon) This is a trial and error method. One teaspoon is a start and you can repeat on a daily basis until a more appropriate level is achieved. Crushed seashells have the same effect and are longer lasting. You can add those in a mesh bag (one cup for 50 Gallons). Again, this is trial and error. Monitor the pH and adjust accordingly. Once the pH is at the desired level, you can add the shells to the substrate, or keep the bag in the filter.

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