Advantages of Growstones Over Hydroton

by Paula Costa, Growstone Consultant for R&D Applications

Growers have had a love hate relationship with Hydroton for years. Now there’s finally a choice. Besides the clear advantage of providing a higher level of aeration than Hydroton, Growstones hold more water, have no fines, and release silica over time in a form plant roots can uptake.

Here are some of the advantages of Growstones aggregates over Hydroton based on actual physical characteristics of both substrates.

1. Higher air-filled porosity.

At field capacity (i.e. after irrigation water has drained away), Hydroton air-filled porosity is about 42%, while Growstones hydroponic media is 48% by volume. This corresponds to at least 12% higher aeration in Growstones than Hydroton. The importance of high porosity in hydroponic growing cannot be undermined.  Ideal substrates have small and large pore spaces. When the substrate is irrigated, water is held in the small pores but quickly drains through the large pores, allowing fresh air to flow through the soil, bringing oxygen to the roots and removing carbon dioxide from the root zone.

2. Significantly higher water holding capacity.

Hydroton is characterized by a very low water holding capacity: 9.6% compared with 29.4% by volume for Growstones hydroponic media. This corresponds to 78% higher moisture content after drainage.

The significance of points 1 and 2 is that Growstones much higher water holding capacity, is not achieved at the expenses of air-filled porosity, quite the opposite, as mentioned in point 1. This is explained by Growstones very low bulk density and corresponding high air-filled porosity.

3. Significantly lower bulk density (lightweight).

Growstones are very lightweight with a bulk density of 0.20 g/cc; while Hydroton bulk density is 0.40 g/cc. This explains Hydroton’s significantly lower water retention since its porosity depends solely on the large pores between Hydroton pellets, which enhances drainage and aeration, but does little for moisture retention. Hydroton high bulk density also has important implications on shipping costs from Germany where it is manufactured.

4. Highly porous substrate with no fines (dust).

Growstones and Hydroton are both fast draining well-aerated hydroponic media. The advantage of Growstones hydroponic media is that it contains almost no fines, oppose to Hydroton characteristic clay fines, which leach out and tend to accumulate at the bottom of the nutrient reservoir. 

5. Growstones release silica in a form plants can uptake.

Growstones are made of 98% vitreous soda lime glass. Therefore, Growstones aggregates contain silica, which leaches out through time into the nutrient solution in a form easily uptake by plant roots. 

As such, Growstones provide a higher level of aeration/oxygen diffusion, with the added advantage of holding a significantly higher amount of water, absence of fines, and release silica over time in a form plant roots can uptake.

Also relevant is the fact that Growstones are made from recycled glass, right here in the USA. Besides the obvious advantages of choosing national products, the Growstones choice significantly reduces waste glass in landfills, clay mining and carbon miles associated with long distance shipping from Germany where Hydroton is manufactured.