Natural aquariums: why the soil on the bottom matters more than you think

I read with interest the first article in a series on natural aquariums. It starts at the bottom, and in particular with the soil, which in this article is not simply a store of nutrients but can become one of the most active environments in the whole tank, if it is designed to be colonized by roots and microorganisms.

The first point is that not every soil is suitable. The right one is a simple mix, made mostly of peat and mature compost, with no added fertilizers. Perlite, coconut fiber and products enriched for horticulture should be avoided. In the first weeks the organic matter releases humic compounds and tannins, and the water can turn amber: that is why water changes, roughly every one to two weeks, serve to help stabilization and not to fight the soil. The article also suggests soaking it first in a separate container, changing the water periodically.

The part I liked most concerns roots. If the bottom stays compact and is not penetrated much, oxygen-poor zones can form in the deeper layers. When roots do penetrate, they form a rhizosphere where plants and microorganisms interact, and the roots can transfer oxygen to the substrate. That is why many rooting plants are needed from the start.

Finally, the author makes clear that soil alone is not enough: stability comes from the combination of substrate, plants, filtration, light and feeding, and reducing interventions does not mean stopping maintenance. A very good starting point for anyone who wants a more balanced aquarium.

Source: AcquaPortal