How much fertiliser does your aquarium need?

We are often asked: “How much fertiliser do I need for my aquarium?”

On all product packaging you find dosage recommendations which give you initial information on how to start the fertilisation. But is this really true for your aquarium?

Be aware that these recommendations never totally match with your aquarium. Why? Unlike with medications and water treating products, dosing recommendations not only refer to the water volume but also to the nutrient absorption of your plants.

The consumption of the nutrients depends on the plant mass, the used species, the set CO2 supply and light quantity and the available nutrients. Due to fluctuations with one of these factors the nutrient uptake of your plant can change immediately. That’s why the correct dosing never can be given as general recommendation. The dosage recommendations are determined for average aquariums and therefore only can guess how your situation is. But don’t worry, the recommendations are structured in a way that no problems can occur – but could you perhaps get more out of your plants?

The dosage serves the purpose to cover the daily consumption of the aquatic plants and to create the water values for the perfect plant growth. Consequently we need to add fertiliser for the ideal water values and for seven days of daily consumption. The plants draw on this depot until the next dosing. We also recommend you use a daily fertiliser to compensate for the plants’ high consumption of special nutrients each day. For this purpose the combination of JBL Ferropol (every 7 days) and JBL Ferropol 24 (daily) has proven its worth.

But keep also an eye on the nutrients nitrate (NO3) and phosphate (PO4). They are essential for the plant growth and should at no time come to 0 mg/l. You can ensure an increase of the value with the combi product JBL ProScape NPK Macroelements or specifically with JBL ProScape N Macroelements and JBL ProScape P Macroelements .

The water values will tell you whether the general dosage recommendations are sufficient or whether corrections have to be made. Test for the iron content with the JBL Iron Test Fe a few hours after the dosing and repeat the measurement 24 hours later and you receive a first impression about the intensity of your plants’ nutrient uptake. If you only dose the fertiliser every 7 days you will need to check the values again before you redose it. If the parameters Fe, NO3, PO4 are 0 mg/l you need to increase the dosage.

To support your fertilisation you can also enter the values into the JBL dosing calculator and receive an evaluation with recommendations for action: Calculador de dosagem ProScape

The ideal water values are:

  • CO2: 20-35 mg/l
  • nitrate (NO3): 10-30 mg/l
  • potassium (K): 10-30 mg/l
  • phosphate (PO4): 0.1-1.5 mg/l
  • iron (Fe): 0.1-0.5 mg/l
  • magnesium (Mg): 5-10 mg/l
  • lumen / litres: 30 – 60 lm

Along with the fertilisation the lighting is an important factor. Check with the Calculador de luz ProScape if your illumination is sufficient.

You can read more about CO2 here: Why is carbon dioxide (CO2) the most important plant nutrient in the aquarium?

© 16.10.2016
Matthias Wiesensee
Matthias Wiesensee
M.Sc. Wirtschaftsinformatik
JBL GmbH & Co. KG

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