Why additional nutrients for aquatic plants?

Our Central European water often differs significantly in its composition from tropical waters. However, it should be borne in mind that there is no such thing as Central European water and that there are sometimes considerable differences in hardness and composition depending on the region. However, it can be generalised somewhat that Central European waters have a higher proportion of calcium and magnesium, whereas potassium is very often only present in small quantities. Trace elements required by plants are very often not present in tap water or only in trace amounts, which are quickly consumed by the aquatic plants in the aquarium.

For this reason, an additional supply of the required trace elements will be necessary for planted aquaria in order to achieve strong, healthy plant growth and at the same time prevent the unwelcome growth of algae.

The running-in phase of an aquarium

After setting up an aquarium, you will usually notice that the aquatic plants grow very vigorously at the beginning and make a vital impression. Depending on the set-up (e.g. with substrate additive), the substrate used and the starting water, this phase can last up to 4 months, sometimes even longer, without additional care. Regular weekly water changes can prolong this phase.
Later on, however, you will notice that initially very demanding plants such as Cabomba caroliniana or Limnophila sessiliflora no longer grow so well and give a sickly impression. This is the latest point at which water changes and fish food no longer supply the aquarium with all the trace elements required by the plants in sufficient quantities.

Supplement nutrients in the event of algae problems?

If you do not start to supply the aquarium with additional nutrients at this point, the appearance of algae, especially beard, brush and filamentous algae, is virtually pre-programmed. In contrast to the "higher" aquatic plants, these "lower" plants are able to manage with fewer trace elements and then exploit gaps in the nutrient supply to establish themselves permanently in the aquarium.

If the water values of such aquaria are measured more precisely, iron deficiency (Fe = 0 mg/l or only detectable in traces), an excess of phosphate (values of 3-5 mg/l are not uncommon) and sometimes (if water changes are neglected) an excess of nitrate (values of up to a multiple of 50 mg/l occur) are very often found.

However, the diagnosis that is often quickly made, i.e. that there is an excess of phosphate and nitrate in the aquarium, is incorrect, as the cause of plant growth problems is more likely to be a lack of iron and, in a broader sense, trace elements, which prevents the "higher" aquatic plants from effectively processing the phosphate and nitrate. Sometimes you hear recommendations such as less lighting in the aquarium or replacing the fluorescent tubes, but these are not correct in terms of content. Without a solution to the problem of supplying the aquatic plants, the aquarist will not achieve a solution to problems with undesirable algae growth or poor growth of aquatic plants.

If you start to change the water regularly and to a greater extent (30% per week) and add iron and trace elements, you will notice after a few weeks that the aquatic plants look more vigorous again and that the algae no longer multiply and spread so quickly. From this point onwards, you can start replanting (or replanting if necessary) some very vigorous species (usually stem plants such as waterweed, hair vetch, Indian water star, etc.). These effectively break down phosphates and nitrates and thus bring the aquarium back into balance. In the second phase, slow-growing species such as some water cups (Cryptocoryne spec.) or Amazonian sword plants (Echinodorus spec.) can also be successfully replanted.