Root Tabs: Targeted Substrate Feeding
How slow-release root tabs deliver nutrients to heavy root-feeding plants in inert gravel and sand, and how to place and replace them.
Overview
Root tabs are slow-release nutrient capsules inserted into the substrate near plant roots. They release minerals over weeks and are used to feed heavy root-feeding plants, especially when the substrate is an inert material such as gravel or sand that holds no nutrients of its own.
What they contain
Root tabs supply a range of nutrients, including magnesium, nitrate, phosphate, potassium, manganese, zinc, molybdenum and iron. This mix targets the root zone rather than the water column.
Which plants benefit
- Cryptocoryne plants
- Sword plants
- Bulb plants
- Carpeting plants and plants that spread by runners
Stem plants can absorb nutrients from either the water or the substrate but generally prefer water-column dosing. Mosses, floating plants, anubias and java fern typically need few or no root tabs because they are not rooted heavy feeders.
How to place them
Push each tab as deeply as possible into the substrate, ideally underneath a plant's roots, working quickly before it begins to dissolve. A common pattern is roughly one tab every 5-6 inches in a grid; densely planted tanks may use spacing closer to every 4 inches. Large plants such as swords benefit from several tabs arranged around their base.
Replacement and deficiency
In inert substrates, tabs are commonly replenished monthly to maintain nutrient levels, and dosing rises as plants mature: a young sword may need one tab every six weeks, while the same plant months later may use several per month. Stunted growth, yellowing, browning or melting leaves can indicate that nutrients have been depleted.
Practical notes
- Concentrate tabs around heavy root feeders rather than spreading evenly
- Push them fully under the substrate to limit nutrient leaching into the water
- Increase dosing as plants grow and demand rises
- Combine with water-column dosing for tanks mixing root and stem plants