Ludwigia arcuata has attractive reddish foliage and is easily trimmed to form dense bushes.
Ludwigia arcuata is a delicate stem aquatic plant that originates from the US. It is often confused with Ludwigia brevipes, which is similar, but slightly larger with broader leaves. It is also similar to Didiplis diandra which is much harder to grow well. Ludwigia arcuata has attractive orange - reddish leaves and thin stems and leaves.
Ludwigia arcuata is tolerant of a wide range of water parameters and is generally an easy background aquarium plant to grow as long as it receives enough light and nutrients. The main issue most folks have with it is that it grows yellowish rather than reddish and many folks also find it difficult to achieve a compact bush. This stem plant grows much redder with nitrate limitation and requires stronger lighting to induce better coloration and more branching. These two aspects are covered further in detail below.
Ludwigia arcuata can be trimmed aggressively. This encourages side shoots to form and the plant can become very bushy. It is quite resilient to being grown densely, and can be pruned for many weeks without requiring replanting. It can be used in aquascaping smaller tanks as mid/background aquarium plants due to its fine texture.
Using a combination of low water column Nitrates and rich substrate N through the usage of root tabs allows deep coloration and yet profuse branching to get good density bushes. Grown with APT Complete and APT Jazz root tabs.
Key success factors
CO2 necessary for coloration and for it to sprout profusely and produce dense bushes.
Sufficient light (80-100 umols of PAR gives lighter orange tones, while upwards of 150 umols of PAR gives redder coloration and more branching).
Nitrate limitation gives much deeper coloration without excessive lighting. Impact starts being visible when NO3 levels <5ppm.
Stronger light (80-100 umols of PAR gives lighter orange tones, while upwards of 150 umols of PAR gives redder coloration).
Stronger red/blue light spectrum.
Low nitrates in the water column causes it to become significantly redder (5ppm and below).
This is one of the plants that exhibit much redder colors under nitration limitation - meaning that the plant grows much redder if it is starved for nitrates. Over-do this and the plant will stunt. Since it is tolerant of much lower nutrient levels than other plants - other plants will usually stunt first.
However, Ludwigia arcuata branches more profusely when it is not too nutrient deprived. Thus, to get good coloration and density at the same time, nitrate limitation must be managed well. Low nitrates in the water column can still be paired with a rich substrate to get good coloration. A good method is by using a richer substrate or ammonia rich root tabs to feed N to the plants through the root zone, while limiting NO3 levels strongly in the water column (to near 0 ppm levels).
Trimming allows Ludwigia arcuata to be trimmed into dense bushes. In the tank above, under slight NO3 limitation it appears orange rather than deeper red. Ludwigia arcuata becomes significantly redder under low NO3.
Cut off top of plant a few inches below the final desired height. Side shoots will sprout from the remaining bottom portion to fill in the area. As the side shoots form, trim away faster growing shoots that poke above the rest. Over time, you will have a nice contoured bush.
This stem plant will grow sideways if there is a lot of light and empty space. Planting a bit more densely at the start - with stems about 1.5cm apart, will encourage them to grow more vertically.