To add a dash of colour this holiday season, consider Ludwigia sp. Red.

Ludwigia sp. Red is widely available, and goes by several trade names: Ludwigia “mini red”, “super red” etc. but they really all refer to the same species. Its leaves also resemble the festive poinsettia, though the two are not related:)

Get the ‘mini’ look this way

The picture below shows Ludwigia sp. Red grown using APT Zero on the left, and APT Complete on the right. Both came from the same parent plant, but with more available nitrogen in the water, the leaves on the right are 3X as large.

How do I get this smaller form?

Ludwigia sp. Red adapts to lower N levels by taking on a more petite form. Importantly, we are using aquasoil- specifically raw organic soil granules, not synthetic pseudo-soils. Aquasoil serves as a nutrient source and storage buffer, so the plant always has access to Nitrogen through its roots. When paired with the APT Zero, which contains all nutrients except nitrates and phosphates, we achieve this miniature form. The aquasoil would deplete naturally over 4-6 months and would require root fertilisation or the addition of new aquasoil then.

The plant was also grown under strong lighting (~90 umols of PAR) which induces the shorter, more compact form. With less light, the plant would grow taller (more quickly) to reach more light, resulting in more elongation.

This tank also had a moderate amount of CO2 injection (around 20ppm). Ludwigia sp. Red can survive in tanks without CO2 injection- read more below.

But comprehensive nutrition is necessary to avoid deficiencies?
Oh yes. In this tank we provided Nitrogen and Phosphorous through aquasoil, and everything else using APT Zero. The result is a plant that is healthy and in perfect form, just overall smaller. Think of it as having a wholesome, balanced diet, but just eating less of everything.

Does it also mean I should dose less than the recommended amount of APT Zero?

Oh no. APT Zero’s recommended dosage is already calibrated so that when paired with aquasoil, you get complete, balanced nutrition in the right proportions.

Any more upsides to this approach?

This strategy of lean water-column dosing paired with aquasoil substrate is one of the most effective ways to keep algae at bay, and would be the antidote for tanks with persistent green-dust algae “GDA” problems.

What about downsides?

This strategy works for Ludwigia sp. Red, Ludwigia arcuata, Ludwigia brevipes, Rotala rotundifolia and its variants (R. H’ra etc.) as these plants are tolerant of low N levels in the water column. The same approach would not work for plants that require higher Nitrogen levels in water, for instance Ludwigia pantanal.

This approach would not work with using sand as a substrate, and would require the aquasoil to be enriched (with root tabs or new aquasoil) after 4-6 months.

What about a tank without CO2?

Ludwigia sp. Red can grow in tanks without injected CO2, but its colour will not be as rich and the form will not be as compact. If you are starting a new tank, it is extremely helpful to cycle the tank before planting. If you are adding the plant to an existing tank, success is highly dependent on the quality of the purchased plant. This is because adapting to a low CO2 environment is never easy, and in simplistic terms, the amount of stored energy in the plant makes a huge difference. A fresh, high quality stalk would have a higher chance of successfully adapting than one that was harvested from less optimal environments.

Above: Ludwigia arcuata on the left of Ludwigia sp. Red has narrower leaves and becomes deep red (vs orange) under this same low-N strategy. While the lower N environment does not affect the colour of Ludwigia sp. Red, it takes on a more petite form. Read more about this strategy of nitrate limitation here.