Growing aquarium plants seems more difficult than keeping fish alone. In order to create an underwater botanical garden from an aquarium, you need a little experience, and at the same time experimenting with greenery. However, getting lush vegetation is possible. The key is to create the right environment and meet the main needs of the plants. It happens, however, that problems arise even in people who are familiar with the topic. One of them is changes in the leaves (discoloration). Where do they come from and how to prevent them?

Fertilization and the availability of artificial light

The reasons for the occurrence of holes in the leaves, weakening of the structure of the leaf blades and generally poor growth are most often associated with poor lighting and nutrient deficiencies. One factor is related to the other. Intensive fertilization will not give the desired results if the aquarium is not lighted artificially for at least a few hours a day. However, the lighting itself will only partially fulfill its function – the plants will grow quickly, but they may be less dense, the shoots will be weaker and elongated. Thus, the plants will become less attractive. Nutrient deficiencies, such as potassium and magnesium, can be strongly felt in plants. When feeding greens, many people focus on nitrogen, which is usually abundant in the aquarium, but underestimates other elements.

Potassium in the plant – macronutrient functions and deficiency symptoms

Potassium is, after nitrogen, the most important element necessary for plant growth. It accounts for 1% of the dry weight of the plant. It supports many physiological processes and is an activator for over 50 enzymes. Deficiencies may occur with too little fertilization, so potash fertilizers or at least multi-component fertilizers should be used. Sometimes the lack of potassium is associated with heavy fertilization with other ingredients, e.g. high content of calcium, magnesium and sodium in the water. Therefore, fertilization should be balanced. Potassium belongs to the group of mobile nutrients, i.e. symptoms of potassium deficiency in plants are first visible on older leaves.

Potassium deficiency in the plant

  • Initially, potassium deficiency is similar to nitrogen deficiency, leaving discolor. The tissues turn yellow over the entire surface of the leaf blade. Then dark rot spots appear on the leaves.
  • If the potassium deficiency is small but persistent, there are small necrotic spots on the leaves in addition to yellowing.
  • With a long-lasting deficiency, growth is stunted. Growths in plants appear to be low in chlorophyll.
  • The new leaf blades are smaller, the plants look stunted.
  • Shoots (stalks) are more fragile, roots are poorly developed. This is especially visible in young seedlings, which can break and flow out.
  • The lack of potassium in plants increases their susceptibility to unfavorable factors – improper temperature, pathogens or damage by organisms living in the aquarium (including fish).

Magnesium for plants – why is it so necessary?

Magnesium is classified as the fourth or fifth most important nutrient for plants. It is a key element involved in photosynthesis. It affects the production of chlorophyll and energy flow. It is an activator of many enzymes. It is most abundant in the older parts of plants. It is considered quite mobile. Magnesium in plants is essential for their proper functioning. Even an excess of magnesium is tolerated by aquarium greenery, although of course you should not overdo it, so as not to disturb the balance and uptake of other compounds.

Effects of a magnesium deficiency in plants

  • Symptoms first appear on older leaves. The gills have chlorosis between the veins (which remain vivid green). The changes are similar in the absence of iron and manganese, but in the case of both indicated elements, they first appear on the young leaves.
  • The areas between the veins turn yellow, then white, get darker and necrotic.
  • Phosphorus deficiency is also often associated with a magnesium deficiency. The lack of magnesium blocks the absorption of iron.
  • The tips of the leaf blades may curl downwards.

The fertilizer doses may be different – it is worth following the manufacturer’s recommendations, and at the same time focusing more on moderation and balance between the ingredients. Often it is better to give too little fertilizer than to over apply it. You have to observe the greenery, test different solutions and remember how important regular artificial lighting is for plants. The desired effect cannot be obtained with fertilizers alone.

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