Scarlet Temple (Alternanthera reineckii) is one of the most visually impactful red aquarium plants available -- a stem plant producing upright stems with broadly oval, slightly pointed leaves whose upper surface is deep olive-red to burgundy and whose underside is an intensely vivid magenta-red to scarlet that reads as striking from any direction. The underside colour is the defining visual quality: when the leaves are viewed at an angle or from below, the pure magenta-red of the lower leaf surface is among the most saturated reds achievable in the planted tank. Unlike Red Ludwigia which delivers warm orange-red, Alternanthera reineckii delivers a cooler, more vivid magenta-red -- a different position in the red spectrum that reads as more intense and more jewel-like at the same lighting conditions. It benefits significantly from CO2 supplementation -- without it, growth is slow and colour is moderate; with it, growth accelerates and colour reaches full saturation. Suitable for medium to high light setups. Safe with all Neocaridina, Caridina, and snails.
EnhancesCO2
72-82FTemperature
Med-HighLighting
What to Expect
Colour, Growth and Light Response
Deep magenta-red to scarlet underside -- the most vivid red in the catalog -- the lower surface of each Alternanthera reineckii leaf carries a pure, saturated magenta-red to scarlet that is more vivid and cooler in tone than any other red plant in the catalog. This colour is visible when leaves are viewed at any angle other than directly from above -- the angled leaf arrangement on each stem means the undersides are partially visible from the front at all times, making the vivid lower surface a continuous part of the plant's display character rather than a hidden quality.
Upper surface is deep olive-red to burgundy -- two-tone character on every leaf -- the upper surface of the leaf is darker and more muted -- a deep olive-red to wine-red that complements rather than competes with the vivid magenta underside. Each leaf reads as two-toned depending on the viewing angle, with the vivid lower surface and the deeper upper surface creating different colour impressions as flow moves the leaves or as the viewing angle shifts.
CO2 dramatically improves growth rate and colour saturation -- without CO2, Alternanthera reineckii grows slowly and colour saturation is moderate -- it remains attractive but growth may be limited to one or two new internodes per week and the magenta-red is less vivid than its potential. With CO2 supplementation, the plant grows noticeably faster, stems extend more vigorously, and the leaf colour reaches full saturation -- the difference between CO2 and no-CO2 expression in this species is more pronounced than in most other stem plants in the catalog.
Iron is the most important nutrient for colour intensity -- consistent liquid iron supplementation is the primary driver of colour depth in Alternanthera reineckii both with and without CO2. Plants receiving daily or every-other-day iron doses produce more intensely coloured leaves that retain their vivid red for longer before the lower leaves fade to green as the plant extends upward.
Slower growth than Hygrophila or Ludwigia -- trimming cycle is longer -- even with CO2 and good light, Alternanthera reineckii grows more slowly than fast stem plants -- a trimming cycle of four to six weeks is typical rather than the two to three weeks of fast stems. This slower pace makes it more manageable as a planted background element that does not require constant maintenance attention.
Group planting creates maximum colour impact -- a single stem provides a colour accent; a group of seven or more stems creates a dense mass of magenta-red that reads as a vivid, unmistakable focal point in the background. The group planting approach concentrates the colour event and makes the magenta-red visible from across the room rather than as a detail requiring proximity to appreciate.
How to Set It Up
Getting Started
1Plant in groups of seven or more in the background -- strip the lowest 3cm of leaves and plant stems at 2-3cm spacing in a dense background group. The vivid colour of Alternanthera reineckii reads as a focal point in direct proportion to the number of stems planted together -- more stems produce exponentially more visual impact than fewer.
2Medium to high light is required -- this plant does not perform well in low light -- position the planting group under the direct output zone of the lighting fixture at medium to high intensity. Low light produces very slow growth and significantly reduced colour saturation -- Scarlet Temple is one of the few plants in the catalog where light intensity is a non-negotiable for achieving the characteristic that makes it worth growing.
3Dose iron-containing fertiliser daily or every other day -- the most impactful single maintenance action for Alternanthera reineckii colour is consistent liquid iron dosing. Daily or every-other-day dosing at the low end of the recommended dose produces better sustained colour than weekly high doses. Start iron dosing from day one rather than waiting for deficiency signs to appear.
4Add CO2 for best results -- or accept slower growth and moderate colour without it -- if CO2 supplementation is part of the setup, Scarlet Temple will reward it more visibly than almost any other plant in the catalog. Without CO2, accept a slower pace and slightly reduced colour saturation -- the plant is still attractive and distinctive, simply less vivid and less fast-growing than its full potential.
Bonus TipScarlet Temple in the background directly behind a group of Anubias Barteri or dark-leaved Bucephalandra on driftwood creates the most striking warm-cool contrast achievable in a planted tank -- the cool, vivid magenta-red of the Alternanthera mass behind the deep, stable green of the Anubias or Buce reads as a maximally contrasted, compositionally complete pairing where the cool red and the cool green pull against each other across the full spectrum distance between them. The contrast is more vivid than red against green because the magenta quality of the Alternanthera red is more spectrally distant from the deep green of Anubias than the orange-red of Ludwigia.
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Browse more aquatic plantsPair Scarlet Temple with Anubias, Bucephalandra, or Vallisneria for a striking planted background. Browse our Aquatic Plants collection.
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