Last updated on December 11th, 2025
Anyone who grows Spirulina knows that success depends on close observation – almost like communicating with a living being. The culture “responds” through its color, density, and overall behavior, especially during unstable weather when conditions swing from one extreme to another.
How I made my unexpected discovery
A few weeks ago, an unusually strong storm hit my area. Overnight, my spirulina culture became cold, thin, and visibly stressed. Realizing I hadn’t cleaned the tank in a while, I decided to give it a full reset: I removed the water pump, air pump, heater, and three volcanic stones that I had placed in the tank a long ago by complete intuition.
My initial reasoning for adding volcanic stones was simple: Spirulina naturally thrives in volcanic lakes. So I collected some stones that seemed appropriate. They had been in the tank for nearly a year without causing issues – but it never occurred to me that they might actually play an active role in the ecosystem. When I put all the equipment back, out of pure laziness, I left the stones out.
The surprising role of volcanic stones
Despite the reset, the culture was deteriorating sharply: the color faded to yellow, the density dropped, and cells were accumulating at the bottom of the tank. I tried different things, and although there were slight improvements, it hadn’t returned to its former vitality.
A couple of days passed, and in desperation, I suddenly remembered the stones and put them back in the center of the tank. Within minutes, the cells began accumulating around the stones, where they could get more light and oxygen. Hours later, the culture had regained its mobility and color, and within a couple of days it was thick, vibrant, and ready for harvest.
How I explain it
My working theory is that the volcanic stones act as a natural stabilizer for the culture. Volcanic rocks are rich in minerals and have a porous structure that influences both pH and micro-circulation within the tank. Even if they don’t release significant minerals into the water, they create a more familiar physical environment – surfaces for micro-organisms to anchor to, micro-currents that improve oxygenation, and a subtle buffering effect that helps maintain Spirulina’s preferred alkaline conditions.
In other words, the stones recreate just enough of Spirulina’s native volcanic-lake ecosystem to support resilience, especially during sudden environmental fluctuations. This explanation still needs controlled testing, but the dramatic before-and-after results make it a hypothesis worth pursuing.
What I learned
Trust your intuition – especially when working with biological systems that don’t always behave according to rigid rules.
Mimicking Spirulina’s natural habitat matters more than I previously realized. The volcanic stones clearly contribute to stability and growth, which opens up fascinating directions for further testing – including experimenting with volcanic plants or other natural elements.
