FlyTrapCare Forums

I recently "discovered" Growstones, an expanded glass product that might be a good, non-floating(?), substitute for perlite. I contacted the company:

I'm interested to know whether your Gnat Nix! would be suitable as part of the medium for my carnivorous plants - not just as a top coat. My main concern is any possible leaching of minerals from your product into the (distilled) water I sit the plants in. I understand that the glass component (SiO2, correct?) should be safe but are any of the chemicals used to create the expansion going to raise the Total Dissolved Solids in my water?

And the reply:

If you rinse Growstones (Gnat Nix or any other Growstone product) really well and then soak them for a 24 – 48 hour period, this should leach out most surface minerals (Calcium, potassium, phosphorous, Silicon), from the surface of the stones.

After discarding the soak water in the garden, and use new DI water, your ppm may still rise slightly initially just from residual minerals inside the deepest pores, but much less than if not rinsing and soaking. At this point you would need to check the ppm and determine if the soluble solids are within the range acceptable for carnivorous plants.

For what it's worth.

They use methane gas to expand their soda-lime-silica glass powder, the calcium from the lime could potentially be harmful as it is basic and almost 11% of glass by weight and VFTs prefer an acidic environment. The potassium should be negligible as it accounts for only 0.3% of glass by weight and I honestly see no reason why phosphorous, which would be bad for the plants, would be in the glass powder at all prior to expansion.