Part I covered the four pillars of plant growth: light, CO2, micronutrients and macronutrients. The next question is how much of each your aquarium needs. The answer depends on the type of tank you run, so the first step is to classify it honestly.
Where do I start?
Fertilisation always follows light and CO2. A brightly lit tank with CO2 injection grows fast and uses a lot of nutrients; a dimly lit tank without CO2 grows slowly and needs very little. Dosing as if your tank were in a different category is one of the most common causes of algae and deficiencies.
Classifying your aquarium
Low-tech
- Moderate light, no CO2 injection
- Slow-growing plants such as Anubias, ferns, mosses and Cryptocoryne
- Small weekly doses of an all-in-one fertiliser are usually enough
Medium-tech
- Medium light with CO2 injection
- A mix of slow growers and easy stem plants
- Regular all-in-one dosing, with single nutrients added if deficiencies appear
High-tech
- Strong light and well-regulated CO2
- Many fast-growing and red stem plants
- Daily dosing, often with separate macro and micro components
Whatever the category, CO2 should be monitored. A CO2 drop checker that turns green shows the right concentration; for setups without a cylinder, LGND C5 Eos can add carbon.
Further nutrients
Besides NPK and iron, plants need calcium, magnesium and a range of trace elements. In hard tap water calcium and magnesium are often present already; in soft or RO water they must be added with a remineraliser such as LGND Evenness. Trace elements are covered by LGND Heaven or an all-in-one product such as LGND Avalon.
Fish provide some nitrogen and phosphate, but in tanks with lots of plants this is rarely enough, and potassium is barely present in fish waste at all. Topping up with LGND Nitrogen, LGND Phosphat and LGND Potassium fills these gaps.
Plant mass
The amount of plants matters as much as the type of tank. A freshly planted aquarium with a few cuttings consumes very little; the same tank fully grown in six months may need several times the dose. Start low after planting, then raise the dose step by step as the plants fill in. A densely planted tank also leaves less room for algae, because healthy plants take up nutrients faster.
Next: in Part III we look at target water values, how to measure your tank’s consumption and the different fertilising systems. To support strong root and shoot growth from the start, LGND Essential can be added alongside your regular fertiliser.