A 78-gallon natural planted tank in New Delhi, India at six months post-setup. The plants are in plastic trays containing ordinary soil hidden behind the driftwood.
Hobbyists should understand that potting soils can become anaerobic
much faster than a clay-rich soil, a loam, or a pure gravel substrate. This
is because potting soil has considerable organic matter for bacteria to
eat (i.e., metabolize). Enhanced bacterial metabolism consumes oxygen
and causes the soil to become increasingly anaerobic. Thus, one must
not make the potting soil layer too deep or block its access to oxygen
by covering it with driftwood, rocks, or a thick layer of gravel or sand.
The resulting anaerobic pockets may inhibit plant growth and produce
compounds toxic to fish.
A potting soil will pull oxygen out of the water, especially during
the first two to eight weeks when decomposition of soil organic matter
is greatest. If plant growth is poor and there is insufficient water
aeration, fish may end up at the surface gasping for air. The solution is
to immediately increase aeration and/or water movement.
Once the soil is submerged, bacterial activity and decomposition will
steadily increase during the first few weeks. This initial soil chaos is a
natural and inevitable process following soil submergence.
3 The soil will
thereupon flood the water with nutrients that can stimulate algal growth.
If there are few plants or the plants are not growing well, this nutrient
flood will stimulate algal growth. Excessive algal growth will inhibit
plant growth, thereby creating a vicious cycle: Dying plants release their
embodied nutrients into the water, further stimulating algae, and dying
plant roots add raw, fresh organic matter to the soil, thereby making the
soil even more anaerobic and inhospitable for plants.
The hobbyist’s overall goal should be to get plants growing well before
the soil chaos. For if plants are growing well during the first two weeks,
plants—not algae—will absorb much of the nutrient release. Plants will be
producing enough oxygen to keep their roots safely oxygenated, and thus
the natural planted tank gets safely established with minimal problems.
A natural planted tank should be set up for maximal plant growth
at the start. Setting up a natural planted tank and then waiting a few
Despite a rocky start to the author’s experiment with using generic topsoil from a home supply store, a strict water-change regimen over time
allowed the soil to settle and the plants to develop.
Tropical Fish Hobbyist www.tfhmagazine.com