Root tabs are small, solid capsules or tablets containing concentrated fertilizer designed to be pushed directly into the substrate of an aquarium. They serve as a direct source of nutrients for heavy root-feeding plants such as Cryptocoryne, Amazon Swords, and Vallisneria. They are essential in tanks with inert substrates like sand or gravel that lack natural nutrients. These tabs provide macronutrients and micronutrients—such as iron, potassium, nitrogen, and magnesium—which are released slowly over several months. They should be replaced every 3–6 months to prevent nutrient depletion and promote lush plant growth.