In 2015, we ran a simple experiment that unexpectedly kick-started our interest in using biochar as a water-filtration medium. At the time, we were asking a basic question: could wood-based biochar rival or even replace activated carbon in aquariums?

Using 500 ml plastic bottles as mini test columns, we filled each with a known weight of carbon and passed dyed water through them — iodine for small molecules, methylene blue for medium ones, and a compost-derived DOM solution to mimic the yellowing that develops in tanks. Despite the simplicity of the setup, the results were revealing. Performance varied widely between products, and once the test was corrected for equal carbon mass, the wood-based biochar granules held their own against commercial pellets.

More importantly, we noticed early signs that porous wood char might also support beneficial microbial activity — hinting at a combined chemical-and-biological “biofilter” mode long before we explored it formally.

That modest bottle test became the seed for everything that followed in our biochar-filter journey.