When people talk about hydroponics, they immediately think of water, nutrients and light. But there is one key element that is often underestimated: the substrate.
The substrate does not feed the plant, but it is crucial for stability, oxygenation, water retention and rooting. To choose it poorly is to start with a handicap.
In this guide we look at the main substrates used in hydroponics, with advantages, disadvantages and practical tips, including what changes with automated systems such as Tomato+.
An expanded volcanic material that is lightweight and very porous.
Excellent root oxygenation
Very high drainage
Does not compact
Retains little water → requires frequent watering
Can generate dust (irritant)
Unstable for large plants
Perfect for propagation, sowing and fast-growing crops.
Expanded mineral similar to perlite, but much more absorbent.
Very high water retention
Maintains constant moisture
Excellent for germination
Too "wet" for many crops
Risk of stagnation and poorly oxygenated roots
Less stable
Ideal when mixed with perlite or fiber to improve hydration.
One of the most widely used substrates in the world.
Excellent balance of water and oxygen
100% natural and renewable
Stable pH
Easy to handle even for beginners
May contain salts if not washed
Requires initial swabbing
Not always sterile
Excellent all-purpose substrate for lettuces, herbs and various indoor crops.
Classic of professional vertical farming.
Inert and completely sterile
Total control over water and nutrients
Very physically stable
Standard formats for NFT, DWC, ebb&flow systems
Not biodegradable
Problematic disposal
Can irritate skin and respiratory tract
Requires pH stabilization
Perfect for large automated plants and constant production.
High-porosity clay pellets.
Reusable many times
Good oxygenation
Highly draining
Perfect for DWC, ebb&flow, hybrid systems
Requires thorough cleaning
Tends to accumulate salts
Does not retain much water
Unsuitable for initial stages
Good as a structural substrate or in support of rooted blocks.
Increasingly used for sustainability and recyclability.
Natural and biodegradable
Good moisture management
Environmentally friendly
High variability
Less suitable for high-precision systems
Possible biological contamination
While many hydroponic systems require the use of complex substrates to manage, Tomato+ has developed Compostable Pods with structure and fibers designed to ensure:
Optimal waterabsorption during germination
Evenly distributed seeds (stable germination)
100% biodegradable materials
Zero contamination because everything is sealed and standardized
Compatibility with the AI reading of the plant and its root state.
This eliminates the problem of substrate choice, reduces complexity for the user, and ensures software-controlled growth conditions.
There is no "best" in an absolute sense. It depends on:
type of planting (manual, automatic, professional)
species grown
ability of the user
frequency of irrigation possible
goal: productivity, simplicity, sustainability
Rock wool → precision and professional productivity
Coconut fiber → versatility and simplicity
Perlite + Vermiculite → great mix for seeding
Expanded clay → recirculated or structural systems
Tomato+ pods → best balance of performance, cleanliness, and automation
Substrate is the basis for growth, and is as crucial as nutrients and light. Understanding the differences allows you to choose the best solution for your hydroponic system.
With Tomato+, complexity disappears: everything is already optimized, standardized, and biodegradable, ensuring stable and predictable growth through integration with software and AI.
Thank you for reading this article. Keep following us to discover new content on hydroponics, vertical farming and smart agriculture.
Tomato+ Team