Editing Hydroponics (section)

===Expanded clay aggregate===
{{Main|Expanded clay aggregate}}
[[File:Hydroton.jpg|upright|thumb|[[Expanded clay aggregate]]]]
Baked clay pellets are suitable for hydroponic systems in which all nutrients are carefully controlled in water solution. The clay pellets are inert, [[pH]]-neutral, and do not contain any nutrient value.

The clay is formed into round pellets and fired in rotary [[kiln]]s at {{convert|1200|C}}. This causes the clay to expand, like popcorn, and become porous. It is light in weight, and does not compact over time. The shape of an individual pellet can be irregular or uniform depending on brand and manufacturing process. The manufacturers consider expanded clay to be an ecologically sustainable and re-usable growing medium because of its ability to be cleaned and sterilized, typically by washing in solutions of white vinegar, [[chlorine]] [[bleach]], or [[hydrogen peroxide]] ({{chem|H|2|O|2}}), and rinsing completely.{{fact|date=March 2025}}

Another view is that clay pebbles are best not re-used even when they are cleaned, due to root growth that may enter the medium. Breaking open a clay pebble after use can reveal this growth.{{Citation needed|date=April 2023}}