When selecting a good liquid fertilizer, look for a supplement with trace elements such as iron, manganese, boron, zinc, etc., and one that has a good ratio of nitrogen (N), phosphorus (P), and potassium (K), otherwise known as the NPK ratio.
While there are many recipes for dosing nutrients, for most basic setups with hardy plants, a liquid fertilizer made by a reputable company will perform well. When selecting a good liquid fertilizer, look for a supplement with trace elements such as iron, manganese, boron, zinc, etc., and one that has a good ratio of nitrogen (N), phosphorus (P), and potassium (K), otherwise known as the NPK ratio. Ideally, a ratio of N with one to two times the K and minimal or zero P is advisable. Plants do require P, but excess can lead to algal blooms and there is usually sufficient P in the aquarium from fish waste and fish food to fulfill the requirements of most plants.