The substrate is the layer your plants live in, so it shapes how well they root, feed and grow. Get the type, depth and feeding right and everything above it becomes easier; get it wrong and you will be fighting poor growth and algae for months.
This guide covers the practical side of aquarium plant substrate: how deep to make it, what your plants actually need from it, when root tabs help, and how to add it to a new tank without a mess.
How Deep Should Planted Tank Substrate Be?
As a rule of thumb, aim for at least 5cm (about 2 inches) where your plants will root. That gives roots room to spread and gives you something solid to push stems and bare-root plants into. If you can manage more, planting becomes easier still.
Many aquascapers slope the substrate, around 7cm at the back falling to 3cm at the front. The slope adds depth to the scape and gives heavy root feeders such as Amazon swords and crypts the deepest zone at the back. Avoid going much deeper than 8–10cm, as very thick layers of soil can trap waste and are harder to manage.
Shallow Tanks and Nano Tanks
In a small tank, a deep slope can eat into your swimming space. Keep around 3–4cm and choose smaller plants, or lean on epiphytes that attach to wood and rock and do not need substrate depth at all.
Nutrient-Rich or Inert: What Do Your Plants Need?
Low-light, undemanding plants such as Anubias, Java fern and mosses grow happily with a plain sand or gravel substrate, because they feed mainly through their leaves. Demanding root feeders, carpeting plants and fast stems do far better on a nutrient-rich planted tank substrate that releases nutrients around the roots.
Tropica Aquarium Soil is a good example of an active soil: it supplies nutrients over the long term and helps support the water conditions many plants prefer. Active soils can also influence pH and hardness, so they suit some tanks better than others. For a full comparison of soils, sand and gravel, read our guide to the best substrate for planted tanks, and see which plants grow in sand if you prefer a sandy look.
Root Tabs: Feeding Roots in Any Substrate
Root tabs are small, nutrient-rich tablets pushed into the substrate close to hungry plants. They are the simplest way to feed root feeders in sand, gravel or an ageing soil. We recommend Neutro TerraTabs, which release nutrients over several months.
Place a tab a few centimetres from the base of each large plant, such as an Amazon sword or Cryptocoryne, and replace them every two to three months. Do not put them right against a plant's roots, and keep them away from shrimp-heavy areas if you are cautious. For help balancing root feeding with liquid feeding, our guide to understanding aquarium fertilisers explains what to add and when.
From Aqua Essentials
Setting up a new planted tank? Our substrates and root tabs are chosen for real-world results in UK tanks.
Shop substrates →How to Add Substrate to a New Tank
Always add substrate to an empty tank. Doing it with water in place is wonderfully messy and almost impossible to shape. Rinse inert sand and gravel until the water runs reasonably clear, but do not rinse aqua soil, as you will wash away nutrients and break the grains down.
Build your slope first, then add just enough water to make the surface damp and tacky. That makes it much easier to push plants in without them floating up. Plant from the back to the front, putting the tallest and hungriest plants in the deepest part. Once planted, fill the tank slowly onto a plate or a plastic bag so you do not disturb your layout.
Looking After Your Substrate
Regular water changes keep waste from building up in the substrate, but be gentle: hover the siphon just above the surface rather than plunging deep into the layer. Whether to vacuum a planted substrate depends on the type, which we cover in should you vacuum the substrate in a planted tank?
Remove dead or dying plant material promptly, and keep feeding steady with a balanced liquid fertiliser from our plant fertilisers range. Healthy plants that have what they need leave less for algae. Most active soils slowly run out of nutrients after a couple of years, at which point root tabs and liquid feeding keep growth going without a full replant.
A good substrate is a one-off decision that pays you back for years. If you are unsure which type or depth suits your plants, take a look at the range at aquaessentials.co.uk or get in touch — our Devon team is always happy to help.
