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Waterwaardes in het Aquarium: Wat Ze Zijn en Hoe Je Ze Beheert

Aquarium Water Parameters: What They Are and How to Manage Them

Water parameters are a crucial, yet often underestimated, part of successfully keeping an aquarium. In this blog post, we'll cover the most important water parameters, what they mean, which values ​​are healthy, and how to adjust them if the balance is disturbed.

With a general test like the 6-in-1 test strips, you can quickly get an idea of ​​the most important values. If you notice a value is too high or too low, always use specific tests for more accurate insight.

📋 Overview of Water Parameters

Below is an overview of the most important water values ​​and what they represent:

  • pH – Acidity

  • GH – Total Hardness

  • KH – Carbonate hardness

  • O₂ – Oxygen content

  • CO₂ – Carbon dioxide content

  • NO₂ (Nitrite) – Toxic intermediate in waste decomposition

  • NO₃ (Nitrate) – End product of waste processing

  • Fe – Iron

  • PO₄ (Phosphate) – Important nutrient for plants

  • NH₃ (Ammonia) – Very toxic to fish

  • NH₄ (Ammonium) – Precursor to ammonia

  • Cl – Chlorine

  • Cu – Copper

  • SiO₂ – Silicate (influence on algae growth)

🧪 Explanation Per Water Value

pH – Acidity

  • Ideal: 6.8 – 7.5 (neutral)

  • Too high: Change water (50%)

  • Too low: use pH increaser

pH significantly influences the living conditions of your fish and plants. Always measure at the same time of day, as pH fluctuates due to light and temperature.

🛠 Tools:

  • pH Minus / pH Plus

  • CO₂ system or liquid CO₂ (e.g. HS Aqua Flora Carbo)

GH – Total Hardness

  • Ideal: 8 – 12 °dGH

  • Too low: Plant growth stops, leaves become slimy

  • Too high: Risk of salt formation, leaf damage

GH determines the amount of calcium and magnesium in the water. This influences plant growth and fish health.

🛠 Tools:

  • GH Plus

  • Liquid plant food

  • Change water (25%)

KH – Carbonate hardness

  • Ideal: 5 – 10 °dKH (7–10 for cichlids)

  • Too low: Unstable pH

  • Too high: Less CO₂ available for plants

KH stabilizes the pH and works in conjunction with CO₂ and GH. Peat in the filter helps lower KH.

🛠 Tools:

  • KH Plus / Minus

  • Peat (in filter)

  • Change water regularly

CO₂ – Carbon dioxide

  • Essential for plant growth

The correct amount of CO₂ depends on pH and KH. You can calculate a guideline yourself.

🛠 Tools:

  • CO₂ system / tablets / liquid CO₂

  • Drop checker / bubble counter

O₂ – Oxygen

  • Essential for fish and bacteria

  • Measure oxygen when your fish are gasping for air or at higher temperatures

Ensure good water circulation and sufficient surface tension (e.g. with an air stone or spray bar).

NO₂ – Nitrite

  • Safe level: 0 mg/l

  • Dangerous from: 0.2 mg/l

Nitrite is very toxic to fish and is formed from ammonia. Too high? Immediately change 50% of the water and measure again the next day.

🛠 Tools:

NO₃ – Nitrate

  • Ideal: < 20 mg/l

  • Too high: Change the water, add plants

  • Too low: Plants may grow poorly

Nitrate is less toxic, but can be harmful in large doses. A well-planted aquarium keeps NO₃ under control.

🛠 Tools:

  • NO₃ Minus

  • Feed less

  • Fast growing plants

Fe – Iron

  • Ideal: 0.1 – 0.5 mg/l

  • Too low: Yellow leaves, poor plant growth

  • Too high: Toxic to fish

🛠 Tools:

  • Iron-rich plant food

  • Change water when there is excess

PO₄ – Phosphate

  • Ideal: 0.1 – 0.5 mg/l

  • Too high: Algae problem

  • Too low: Poor CO₂ absorption by plants

🛠 Tools:

  • PO₄ Minus / Plus

  • Sera Phosvec (in filter)

  • Feed less / remove waste

NH₃ – Ammonia

  • Highly toxic, should be 0

  • Occurs at too high temperatures/pH and from rotting waste

🛠 Approach:

  • Immediately change 50% of the water

  • Ensure good biological filtration

  • Test with separate NH₃ test kit

NH₄ – Ammonium

  • Not directly toxic , but at high pH → conversion to ammonia (NH₃)

  • Too high indicates polluted water or overpopulation

🛠 Approach:

  • Change water

  • Reduce feeding

  • Keep the soil clean

Cl – Chlorine

  • Max. value: < 0.02 mg/l

  • Comes from tap water and is harmful to fish and bacteria

🛠 Solution:

  • Always use a water conditioner such as Tetra AquaSafe / Sera Aquatan

  • Preferably let water stand for 24 hours before use

Cu – Copper

  • Toxic to shrimps and snails from 0.3 mg/l, to fish from 1.0 mg/l

🛠 Solution:

  • Change water

  • Use copper absorbing filter media

  • Use water conditioner that binds copper

SiO₂ – Silicate

  • Promotes algae growth from 0.4 mg/l

  • Non-toxic to fish or plants

🛠 Solution:

  • UV filter against algae growth

  • Clean filter maintenance

  • Flora Carbo Power as an algae inhibitor

🔧 Helpful Tips

  • Don't rely on gut feeling. Test first, then take action.

  • Test regularly, especially with new aquariums.

  • Invest in a good droplet test kit for accuracy.

  • If problems persist, please contact us.

📦 Useful products


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