Liquid Fertilizers

Liquid fertiliser gives plants the nutrients that fish waste and tap water alone do not cover. Plants need macronutrients – nitrogen, phosphorus and potassium – and small amounts of micronutrients, above all iron. If one of them is missing, growth stalls even when there is enough light and CO2.

An all-in-one fertiliser contains everything in one bottle and is easy to dose. Separate macro and micro fertilisers let you fine-tune the dose, for example adding only potassium when a test shows enough nitrate and phosphate. Liquid carbon helps in a small tank without a CO2 system but does not fully replace one.

Start with a smaller dose than the label suggests and increase it gradually while watching the plants and algae. With the EI method a large part of the water is changed weekly so that excess nutrients do not build up. Keep fertilisers dark and cool.