How to grow Rotala Rotundifolia

Rotala rotundifolia is a fast-growing aquarium plant that has long been popular in the planted aquarium world. It was first introduced around 1960 under the misnomer Rotala indica, a confusion that persists to this day; the true Rotala indica is a different plant. Native to Southeast Asia, it is undemanding and grows across a wide range of tank conditions, from simple low-tech tanks to high-tech CO2 setups. Rotala rotundifolia is categorized as easy to moderate difficulty for care, suitable for beginners. This guide will demonstrate the growth and usage of different Rotala rotundifolia varietals, and show aquarium hobbyists how to grow them well.

There are many varieties of Rotala rotundifolia, and their form and color shift with conditions, which is why the same plant can look very different across photos. Rotala rotundifolia red, R. H'ra, R. Ceylon, and R. colorata are the classic red-capable relatives. 'Orange Juice' leans toward warm orange and yellow tones. The one worth pointing out is Rotala rotundifolia 'Blood Red', often labeled the 'SG' or Singapore variant: it reds up far more easily than the others, without needing hard nitrate limitation to get there, which makes it the better choice for most tanks. Most of the reddish Rotala rotundifolia varietals require nitrate limitation to have vivid red coloration. Rotala 'blood red' is the only one that turns red even when nitrate levels are kept high.

Rotala rotundifolia is hardy and takes trimming well, allowing it to be shaped into nice bushes easily. As a vigorous stem plant it takes up excess nitrogen compounds from the water column, oxygenates the tank through photosynthesis, and provides cover for fish and shrimp.

Quick answers:

• Rotala rotundifolia is a fast-growing, beginner-friendly stem plant that is easy to grow and tolerant of a wide range of water parameters.

• It is suitable for both low-tech and high-tech tanks. Carbon dioxide (CO2) injection and good light levels give better coloration and bush density.

• Stronger red coloration comes from higher light intensity and nitrate limitation, not from adding more iron. The 'blood red' varietal does not require nitrate limitation to show off red tones.

• Target roughly 100 umols of PAR and above. Keep water-column nitrates kept low for more intense color in colored variants.

• Prune taller buds often, and allow the rooted portion to sprout side shoots to form a dense bush.

• Propagate by topping healthy stems and replanting. Even cuttings as short as a couple of inches will grow into new plants.

Rotala 'blood red' is used as a background bush in this aquascape.

What Water Parameters Does Rotala rotundifolia Require?

On water parameters, Rotala rotundifolia and its many variants are very hardy plants. It grows well in both soft or hard water. It grows in the range of 1 to 20 dGH, 1 to 16dKH. In grows well in the pH range from 5.0 to 8.0, with a temperature range of 20 to 30°C. Extremely high alkalinity or salinity can affect its growth, and it stunts more easily in such conditions.

As with most aquatic plants in the hobby, it prefers softer water when possible and cooler temperatures give nicer growth forms. It will grow with shorter internodes, larger leaves and branch more readily at 24 degree Celsius compared to 30 degrees Celsius.

Does Rotala rotundifolia need high light and CO2?

Rotala rotundifolia needs more light than shade plants such as Anubias and Cryptocoryne species to grow well. However, it will still grow even if light levels are moderate. It will begin to gain good color above 100umols of PAR. Below this light level, it will grow, but coloration will be less red. More intense light can sun tan the varietals into more intense red tones. However, for varietals that require nitrate limitation to turn reddish (such as Rotala H'ra, Rotala colorata, Red Rotala), nitrate limitation has a greater impact on red coloration than light intensity.

Rotala rotundifolia variants tolerate low Carbon dioxide (CO2) levels well and can be grown reasonably easily in low tech aquariums. However, CO2 injection greatly increases branching growth, and is required for bushes to gain good density. Rotala rotundifolia grown without CO2 injection results in more single vertical stems and even regular trimming does not produce enough side shoots for a dense bush to be formed. So while CO2 is not strictly necessary to grow this plant, it is needed to grow it to dense bush form.

It is not picky about nutrients, but similar to all other aquarium plants, having a comprehensive nutrient dosing approach improves plant health, color and form.

How to Get Rotala rotundifolia Redder

Start with aiming for healthy plants. This means having a stable growth environment, allowing the plant enough time to adapt, and then having a comprehensive fertilization regime that covers all angles. Then having stronger light and nitrate limitation will give stronger reds.

• Strong light and a good display spectrum. 100 umols of PAR, as measured on the aquarium substrate, will be sufficient light to color up the plant. However, light only goes so far for varietals that require nitrate limitation to be red. For common varietals like Rotala H'ra, Rotala rotundifolia red, high light alone will not induce deep red coloration in the plant without Nitrate limitation.

• Nitrate limitation. Keep water-column nitrate (NO3) low, around 5 ppm and below. For the deepest reds, water column NO3 needs to bottom out completely. This will induce deep reds in varietals such as Rotala rotundifolia red and Rotala H'ra. Running the aquarium with very lean nitrates may affect other plants in the aquarium. One way to counter balance low water column nitrate levels is by using a rich substrate that plants can draw nitrogen from with that roots. Since nitrate only needs to be limited in the water column for plants to show the effects of nitrate limitation, one can always pair this with a rich substrate.

In this bush above, you can pinpoint the exact time when the tank water column has become nitrate limited. The new leaves produced during nitrate limitation are significantly redder.

Rotala rotundifolia variants turns greenish when it has plenty of nitrogen and red when nitrogen in the water column runs lean.

Two common myths:

• 'More ferts help': a richer dosing approach can keep the plant healthy but may cause the plant to grow more green, not red if the amount of nitrates in the water is high. 
• 'Add iron': adding more iron will not make the plant redder: iron enables pigment production but does not stimulate it. If you want more red, reach for light, spectrum, CO2, and lower nitrates, simply adding Iron will not help.

How to Trim and Prune Rotala rotundifolia

Stem plants grow continuously toward the light, and Rotala rotundifolia will reach the top of even tall aquariums; left alone it can pass 50 cm and eventually break the surface to grow emersed leaves and flowers. In a high-light tank with space around them, stems tend to grow downward and creep along the substrate. Planted in a crowded area, they grow more upright and vertically. The plant branches more when it is in rapid growth mode, and grows more vertically with less branching when growth conditions are lean. It branches much more when CO2 availability is high.

Rotala rotundifolia takes well to pruning and forms dense bushes, and pruning is what builds that compact, bushy form. It can be cut for many cycles before it needs replanting with fresher tops, which makes it useful for aquascapes where the crest line has to hold a set height.

Prune first about four inches below the final height you want the tops to sit. The canopy should be trimmed with a slope from front to rear as shown in the picture below. As they grow out, cut the shoots that are outrunning the rest; this pushes the shoots below to branch and the canopy to thicken as it climbs. Once the canopy reaches height, keep thinning by removing the tallest shoots and letting new growth replace them, roughly every three days. If the whole canopy starts creeping upward, reset: cut the shrub much lower and let the tops grow out again.

Watch the underside. Overgrowth shades the lower leaves, and shaded leaves drop, so a bush left too long hollows out from below. Over months the old undergrowth deteriorates past saving; at that point let the tops grow long and replant the whole shrub. Running the tank lean also slows overall growth and cuts down how often you need to prune.

Rotala rotundifolia can recover from bare lower stems as it is a very resilient plant. The panel on the left shows a deep trim that leaves bare stems behind, and the right panel above shows the recovery after 3 weeks.

How to Propagate Stem Plants Such as Rotala rotundifolia

Propagation is simple: cut a few inches off the top of a healthy stem and replant it. New shoots sprout from the nodes on the remaining stem, so if the parent plant is healthy you can cut off most of it, leave stems a few inches high, and let them resprout. Even when you want a dense bush, plant the stems at least half an inch apart to leave room for side shoots; let the lower layers stay open even under a thick upper canopy.

Rotala rotundifolia in Low-Tech vs High-Tech Tanks

Rotala rotundifolia flourishes in both low-tech and high-tech aquarium setups. In a low-tech tank, most Rotala rotundifolia variants will grow well, but expect greener, thinner, less branched growth and more skill required to keep it healthy in a carbon-limited environment. Using the variant Rotala 'blood red' is highly recommended, as it grows red much more easily than other variants.

With CO2 injection, the plant will branch much more profusely, which allows the bush to be shaped into high density more easily.