Planted Tank Substrate: Aqua Soil vs Gravel vs Sand (Part 1 of 4)

Mayur Dev|12 अक्तूबर 2026

The substrate you choose is the foundation of your planted tank, and the hardest thing to change later. Compare aqua soil, gravel and sand, learn the right depth and setup steps, and find out when root tabs make the difference. Part 1 of our Planted Tank Series.

Light, CO2 and fertilizer get all the attention. Substrate gets chosen once and then lives with you for years. A planted tank rests on four pillars: substrate, light, nutrients and CO2. This four-part Planted Tank Series covers them in order, and we start with the one that is hardest to change later.

The Four Pillars of a Planted Tank

Substrate: anchors roots and can supply nutrients.
Light: the energy plants use to grow.
Nutrients: the fertiliser that feeds the leaves and roots.
CO2: the carbon plants build their tissue from.

The four must stay in balance. Push one hard without the others and algae takes the opening.

Your Three Substrate Options

Type	Pros	Cons	Best for
Inert gravel or sand	Affordable, stable, does not change your water	No nutrients, so you need root tabs	Beginners, low-tech tanks, hardy plants
Aqua soil (nutrient-rich)	Feeds roots, supports stems and carpets, slightly softens water and lowers pH	Costs more, releases ammonia in the first weeks, typically needs replacing after 1 to 2 years	Carpeting plants, high-tech tanks
Layered (nutrient base plus inert cap)	Nutrition without the full cost of soil	More work to set up	Large tanks, heavy root feeders

How Deep Should the Substrate Be?

For most planted tanks, aim for about 5 to 7 cm at the back, sloping down to about 3 cm at the front. The slope adds depth to the scape and carries debris towards the front where it is easy to siphon. Deeper is not always better, because very deep gravel can develop stagnant pockets.

Setting Up Without Mistakes

Rinse inert gravel or sand until the water runs clear.
Aqua soil: follow the pack. Most aqua soils should not be washed, because that breaks the granules.
Push root tabs under heavy root feeders before planting.
Fill slowly by pouring water onto a plate or bowl so the substrate stays in place. Use water treated with Sunken Garden Anti-Chlorine.
Expect ammonia from aqua soil for the first few weeks. Do regular water changes and test often. Our Nitrogen Cycle series explains how to manage it.

A Note for Soft-Water Cities

Aqua soil lowers pH and softens water. If your tap water is already very soft, as it often is in Mumbai, a soil tank with CO2 can drop pH too far. Read GH, KH and TDS in Indian tap water before you decide.

Feeding the Roots: Root Tabs

Swords, cryptocorynes and vallisneria feed heavily through their roots. In an inert substrate, they will starve without help. Place root tabs close to their base, using the spacing on the pack. Root Boost+ from our Plants Right Series is made for exactly this.