How much light does Anubias need in an aquarium?

Anubias does best with roughly 20 to 40 µmol/m²/s PAR at the leaf surface, which most low-tech and mid-tech LEDs produce at 30 to 50 percent intensity in standard-height tanks. It tolerates readings from about 15 up to 60 µmol when shaded or paired with fast-growing plants. Stock kit LEDs are usually sufficient; you rarely need a high-PAR fixture dedicated to Anubias alone.

Can Anubias survive in low light?

Yes. Anubias evolved in shaded African forest streams and is one of the most low-light-tolerant aquarium plants. It can survive for years at 10 to 15 µmol/m²/s, though growth becomes very slow - sometimes one new leaf every few months. For visible steady growth, aim for 20 to 40 µmol rather than the absolute minimum.

What happens if Anubias gets too much light?

Excess light rarely speeds Anubias growth meaningfully. Instead it triggers algae on leaves that take weeks to replace - especially green spot algae and black beard algae. You may also see yellow or pale new leaves, cupped or gnarled growth, and algae concentrated on the Anubias while shaded areas stay cleaner. Fix it by lowering intensity, shortening photoperiod to about 6 hours for two weeks, and adding shade from floating plants or hardscape.

How many hours of light does Anubias need per day?

Six to eight hours per day suits most low-tech Anubias tanks, with seven to eight hours being the common sweet spot. Mixed high-tech tanks with shaded Anubias placement can run eight to ten hours, but only if the plant itself is not in the brightest zone. If algae appears on the leaves, drop to six hours immediately and reassess after two weeks before increasing duration again.

Why does Anubias get algae on its leaves?

Anubias grows slowly, so each leaf stays in place for weeks or months - giving algae spores time to attach and spread. Excess PAR, long photoperiods, and unused nutrients in the water all accelerate that process. The reliable fix is reducing light intensity and duration, shading the rhizome, trimming badly affected leaves, and adding safe grazers such as Nerite snails or Amano shrimp - not scrubbing with metal tools or doubling fertilizer.

Anubias Light Requirements: PAR, Photoperiod, and Algae

Anubias needs low to medium light - roughly 20 to 50 µmol/m²/s PAR at the leaf surface and a 6 to 8 hour daily photoperiod in most low-tech tanks. That single sentence covers what most aquarists search for, but the useful part is knowing why those numbers work, how to measure or estimate them without expensive gear, and what to change when green spot algae or black beard algae shows up on leaves that barely grow. Anubias is not a plant you light like a carpet of Monte Carlo or a red stem farm. It is a shaded-stream epiphyte that rewards restraint.

This guide walks through PAR targets adjusted for tank depth, photoperiod rules for mixed and single-species setups, the difference between Kelvin and usable light, shade strategies that mimic rainforest canopy, fixture choices from stock LEDs to dimmable planted-tank lights, and a step-by-step plan for dialing in light on a new tank without triggering an algae bloom.

Why Anubias Tolerates Shade Better Than Most Aquarium Plants

Native habitat and slow metabolism

Anubias barteri and its dwarf cultivar, Anubias barteri var. nana, come from shaded waterways in West and Central Africa - Cameroon is the type locality for the nana variety, according to the Flowgrow aquatic plant database. In nature the rhizome anchors to rock or wood along stream margins where forest canopy filters sunlight. Leaves are thick, waxy, and slow to replace. That biology is why Tropica and most hobby references classify Anubias as an easy, low-demand plant: it does not need - and often does not want - the intense PAR that drives fast stem growth.

Flowgrow notes that Anubias grows under very low light (below 0.25 W/L) and also under strong light (above 1 W/L), but the database explicitly recommends placing the plant in a shadier part of the aquarium when light is strong. The plant survives bright conditions; it just pays for that survival with algae on leaves that take weeks to shed.

What low-to-medium PAR means in a planted tank

Aquarium writers use low light to mean roughly 15 to 50 µmol/m²/s PAR at the substrate or leaf, depending on the source. Canton Aquatics groups Anubias with Java Fern and Java Moss in the 15–30 µmol low-light band, while the Aquarium Co-Op PAR guide places Anubias and Cryptocoryne in the 10–20 PAR low category. The spread is normal - fixture spread, water clarity, and measurement height all shift readings.

For Anubias, treat low-to-medium as 20 to 50 µmol/m²/s at the leaves you care about, with 20 to 40 µmol as the comfortable daily operating zone and anything consistently above 60 µmol without shade as high-risk for algae on slow epiphytes.

Target PAR Levels for Healthy Anubias

The 20–50 µmol range and where sources agree

PAR - photosynthetically active radiation, measured in micromoles per square metre per second (µmol/m²/s) - is the only metric that describes light plants actually use for photosynthesis. Watts tell you electricity draw. Lumens describe brightness to human eyes. Kelvin describes colour temperature. None of those replace PAR.

Independent references converge on a similar band for Anubias:

|| Light level | PAR at leaf (µmol/m²/s) | Typical Anubias response | || --- | --- | --- | || Very low | 10–20 | Survives; new leaves may appear every few months | || Ideal | 20–40 | Steady growth; one new leaf every 2–4 weeks | || Tolerated | 40–60 | Works with shade, fast competitors, or stable CO2 | || High-risk | 60+ | Algae on leaves unless heavily shaded or balanced high-tech |

Royal Oak Aquarium Shop’s Anubias care notes recommend 15–40 PAR with 6–8 hours of light. Canton Aquatics groups Anubias in the 15–30 µmol low-light band. If you lack a PAR meter, start a dimmable LED at 30 to 50 percent power in tanks 45 cm deep or less, run 6 hours, and observe for two weeks before increasing anything.

Depth, fixture height, and tank geometry

Light intensity drops with depth. A fixture delivering 70 µmol at the water surface may deliver only 25 µmol at the substrate of a 45 cm tank - which can be perfect for a foreground Anubias - while the same fixture fries a nana tied to wood near the surface. Always think about PAR at the leaf, not at the glass top.

A practical depth cheat sheet:

Shallow tanks (under 30 cm): Stock or budget LED often sufficient; dim if algae appears on upper leaves.
Standard height (30–45 cm): Aim for 20–40 µmol at the Anubias leaf; use fixture height and hardscape placement to fine-tune.
Tall tanks (45 cm+): Either raise Anubias on tall driftwood toward mid-level light, or accept very slow lower-tank growth and rely on shade from above rather than cranking intensity.

If lower leaves stay dark green but never produce new growth while upper leaves get GSA, you likely have a gradient problem - not too little light overall, but the wrong light at the rhizome.

Photoperiod Basics for Anubias Tanks

Six to eight hours for low-tech setups

Anubias does not need a long day. For tanks without CO2 injection and without demanding stem plants, 6 to 8 hours of light per day is the standard recommendation across Anubias-specific guides and general low-tech planted-tank advice. Gensou and Royal Oak both land on 6–8 hours; Canton Aquatics lists 6–8 hours as ideal for low-light plants.

Use this decision frame:

Anubias-focused or low-tech community tank: 6–8 hours
Mixed tank with shaded Anubias and faster stems: 8–10 hours only if the Anubias sits under hardscape or floating plants
Algae on Anubias leaves: drop to 6 hours for two weeks, add shade, then reassess

Photoperiod controls algae as much as intensity does. An extra two hours of light does not make Anubias grow noticeably faster - it gives algae more time to colonise leaves that the plant replaces slowly.

Timers, consistency, and the fish-lighting myth

Fish do not need 12 hours of aquarium light. Most species tolerate 8–10 hours without issue. The habit of leaving lights on “for the fish” while Anubias sits in the tank is one of the most common causes of green spot algae on epiphyte leaves. A USD 10 outlet timer is the highest-return Anubias accessory: set the photoperiod once, keep it identical every day, and stop manual on/off drift that stresses both plants and fish.

If your room has strong ambient daylight hitting the tank glass, count that as bonus PAR and shorten the artificial photoperiod accordingly. Tanks near sunny windows often need 6 hours of LED even when the dial reads “low.”

Spectrum, Kelvin, and What Actually Drives Growth

Once PAR and photoperiod are set, spectrum matters less for Anubias than marketers suggest - but it still affects how the tank looks and how obvious algae appears. Full-spectrum LEDs with strong red and blue output support photosynthesis efficiently. A 6,000 to 7,500 K daylight profile renders the deep green of Anubias naturally and is easy to live with visually.

Kelvin does not replace PAR tuning. A cool 10,000 K fixture can still deliver damaging PAR at the leaf; a warm 4,000 K fixture can deliver perfect PAR for Anubias. Choose spectrum for viewing preference after intensity and duration are correct. Higher Kelvin (bluer) can make GSA dots more visible; lower Kelvin (yellower) can flatten the plant’s green - neither changes growth rate meaningfully if PAR stays in range.

Recognizing Too Little Light on Anubias

Anubias is forgiving, but “low light” is not “no light.” Below roughly 10 to 15 µmol/m²/s at the leaf, growth can stall for months and older leaves may slowly melt at the edges as the plant reabsorbs tissue. Watch for these patterns:

Leaves turn very dark, almost black-green. The plant stacks chlorophyll to capture scarce photons - the opposite of the pale yellow you see with too much light on other species.
No new leaves for many weeks on an established rhizome that is otherwise stable and not recently moved.
Old leaves go transparent or soft at the margins while the rhizome stays firm - distinct from rhizome rot caused by burial in substrate.
Algae still appears despite “low” settings - because unused nutrients in the water column can feed algae even when Anubias growth is minimal.

The fix is modest: raise the Anubias 2–3 cm on hardscape, increase dimmable intensity by 10 percent, or extend photoperiod by one hour - never all three at once. Reassess after two weeks.

Recognizing Too Much Light on Anubias

Excess light is the more common failure mode because beginners equate “healthy plants” with “bright tank.” Symptoms usually appear within days to a few weeks:

Green spot algae (GSA): hard, dark green dots 1–3 mm across that will not wipe off with a finger.
Black beard algae (BBA): grey-black tufts on leaf edges and rhizome - stubborn and almost always linked to light plus imbalance.
New leaves emerge pale or yellow while older leaves stay green - light stress overlapping with possible iron shortage; fix light first.
Leaf cupping, pinching, or gnarled new growth on varieties that normally produce flat oval leaves.
Algae blooms concentrated around the Anubias while shaded corners stay cleaner - a geographic clue that local PAR is too high.

First response: lower intensity, shorten photoperiod by 1–2 hours, and add shade. Do not reach for algaecides or aggressive metal scraping. A soft toothbrush, a razor blade held flat against the leaf, or trimming the worst leaf at the rhizome is enough while light corrections take effect.

Algae on Anubias Leaves and How Light Feeds It

Why slow growth makes algae worse

Fast stem plants such as Rotala or Hygrophila outpace algae by producing new leaves every few days. Anubias replaces a leaf every two to four weeks under good conditions - sometimes slower. Gensou Aquascaping notes that slow leaf development gives green spot, black beard, and dust algae weeks of stable surface and steady light - exactly what they need. The waxy cuticle that protects Anubias from damage also gives spores a durable landing pad.

High light does not speed Anubias growth enough to outrun algae. It mainly raises the energy available to algae while the plant’s metabolism stays capped by its genetics and, in low-tech tanks, by available CO2.

A practical two-week light reduction plan

When algae colonises Anubias leaves, run this sequence before changing fertilizers or CO2:

Set photoperiod to 6 hours for 14 days.
Reduce dimmable fixture output to 30–50 percent if possible.
Move or remount the rhizome into shade - under a driftwood overhang, behind rock, or beneath Amazon frogbit or water sprite.
Trim the worst affected leaves at the rhizome so the plant invests in clean tissue.
Add safe grazers: Nerite snails, Amano shrimp, or Otocinclus - all graze biofilm without tearing Anubias leaves when stock levels are reasonable.
After two weeks, if algae has not spread, return to 7–8 hours gradually - one hour per week - while watching new leaves.

Spot-treating a mature leaf with dilute hydrogen peroxide for 30 seconds is a last resort for stubborn GSA; rinse the leaf in tank water afterward. Skip this on young or variegated leaves that damage easily.

Shading Anubias Without Starving It

Shade is not failure - it is habitat matching. Floating plants diffuse overhead light into the dappled pattern Anubias evolved under. Amazon frogbit, dwarf water lettuce, red root floaters, and water sprite all work. A 30 to 50 percent floating cover often drops effective PAR at mid-tank by enough to keep epiphytes clean while stems below still receive usable light.

Hardscape shade works without live floaters. Mount the rhizome on the underside of a branch, the back face of a tall stone, or the lower third of a vertical wood stack. In high-tech tanks running 80+ µmol for carpets, shaded Anubias placement is mandatory - not optional - if you want algae-free leaves without constant scrubbing.

Flowgrow’s database mentions that high phosphate (1.5–2 mg/L) can induce flowering and that good iron and micronutrient supply combined with high phosphate may reduce spot algae under strong light - but for most hobbyists, shade plus moderate light is simpler and more reliable than chasing phosphate targets.

Picking an LED Fixture for Anubias-First Tanks

Anubias rarely justifies an expensive light purchase on its own. Three tiers cover real-world setups:

Stock kit LED: Usually adequate. Anubias, Java moss, and Cryptocoryne often thrive unchanged. You will not grow a dense HC carpet on the same schedule.
Budget non-dimmable strip (roughly USD 20–40): Fine for Anubias-only or epiphyte scapes. Control photoperiod with a timer; you cannot dial intensity down when algae appears except by raising the fixture or adding floaters.
Dimmable planted-tank LED (USD 50+): Worth it for mixed tanks. Run 30–50 percent for shaded Anubias zones and higher output where stems need it - achieved through placement and shade, not multiple fixtures.

Brand examples hobbyists commonly use in low-to-medium PAR roles include NICREW SkyLED-class fixtures for beginner tanks and Fluval Plant or Finnex-tier dimmable units for mixed planting - but the decisive features are dimming, timer compatibility, and even spread, not the logo on the housing.

Anubias Compared to Java Fern, Buce, and Crypts

Anubias is often grouped with other “easy” epiphytes and shade lovers. Light needs overlap but are not identical:

|| Species | Ideal PAR (µmol/m²/s) | Typical photoperiod | Algae risk under excess light | || --- | --- | --- | --- | || Anubias barteri / nana | 20–40 | 6–8 hours | Very high | || Java fern (Microsorum pteropus) | 20–40 | 7–9 hours | Moderate | || Bucephalandra | 20–40 | 6–8 hours | Very high | || Cryptocoryne (most) | 30–50 | 8–10 hours | Moderate |

If your settings keep Anubias clean, Java fern and Buce usually thrive too. Cryptocoryne may want slightly more PAR and a longer day. Adding red stem plants or carpets without shading your Anubias is when mixed-tank light planning breaks down - solve it with position and floaters, not by blasting the entire tank brighter.

Conclusion

Anubias light management boils down to restraint: 20 to 40 µmol/m²/s at the leaf, 6 to 8 hours of light per day in most low-tech setups, and shade whenever intensity or tank mates push PAR higher. The plant is slow by design; your job is to keep its leaves algae-free while it produces new growth on its own schedule.

If algae appears on Anubias, assume light is too strong, too long, or both until proven otherwise - lower intensity, shorten the photoperiod, add floating or hardscape shade, trim affected leaves, and wait two weeks before changing anything else. That sequence resolves most Anubias lighting problems without expensive gear or chemical shortcuts, and it is the difference between a rhizome that looks good for months and one that becomes a permanent algae display.

When to use this page vs other Anubias guides

Anubias overview - Start here for whole-plant context before deep-diving this topic.
Anubias problems hub - Jump to symptom-specific fix guides when this care topic does not resolve the issue.
Not Enough Light on Anubias - Escalate here when light adjustments are not enough.
Leggy Growth on Anubias - Escalate here when light adjustments are not enough.

Anubias Light Requirements: PAR, Photoperiod, and Algae Control