Planted-tank light spectrum & the WEEK AQUA tunable range: a shelf-ready customer explainer

Spectrum is the colour content of your light, and for a planted tank it decides two things at once: how efficiently the plants photosynthesise, and whether a red Rotala reads crimson or muddy brown. Kelvin is a single-number summary of how warm or cool the white looks; it tells you almost nothing about the underlying spectrum. A tunable fixture such as WEEK AQUA’s RGB+UVA P Series lets you move the colour mix on purpose, which turns spectrum from a fixed factory decision into a working control over growth, plant colour, and even algae. This guide separates the marketing from the physics so you can specify the right light, not the prettiest box.

This is written for the trade and for serious hobbyists: shop owners advising customers, aquascapers speccing builds, and wholesale buyers comparing fixtures across price tiers. Spectrum is where a lot of money is spent on the wrong claim. We cover what plants actually absorb, why Kelvin is the wrong number to shop on, how RGB and WRGB fixtures build their light, what colour rendering (CRI) really costs you, and exactly what a tunable WEEK AQUA fixture does when you open the app. Intensity (PAR) and scheduling are covered in their own guides; here the subject is colour.

Spectrum vs Kelvin: two different questions

The most common mistake on a planted-tank spec sheet is treating colour temperature as if it described the light’s spectrum. It does not.

What spectrum means

Spectrum is the full distribution of a light’s output across wavelengths, from roughly 400 nanometres (deep blue-violet) to 700 nanometres (deep red), with ultraviolet just below and infrared just above. Two lights can look identical to your eye while carrying very different energy at each wavelength. That difference is invisible to you but not to a leaf, because plant pigments respond to specific wavelengths, not to the overall “white” your eye averages out.

What Kelvin means, and what it hides

Colour temperature in Kelvin describes only how warm or cool the white appears: a 2700 K light reads warm and yellowish, 6500 K reads as neutral daylight, and anything above about 10000 K reads cold and blue (2Hr Aquarist). For commercial lamps, the 5000–8000 K range produces a neutral white tone; below 3000 K is warm white; above 10000 K is bluish (Aquarium Gardens).

The catch is that Kelvin is a summary, not a recipe. Two bulbs rated at the same 6500 K can have completely different spectra and therefore grow plants differently; how well a light grows plants depends on its usable spectral output, not its colour-temperature label (2Hr Aquarist). A 6500 K rating tells you the light will look like daylight. It does not tell you how much red or blue energy is in there, and red and blue are where plants do most of their work.

So why is 6500 K the default everyone quotes?

Because it is a sensible, safe aesthetic choice that happens to contain a broad balance of wavelengths. Plants grow well in roughly the 5000–10000 K range, with 6500 K widely treated as the reference daylight colour for a natural planted look (Aquarium Gardens). But “6500 K” is shorthand for “neutral white, broadly balanced,” not a guarantee of growth performance. Treat Kelvin as the look, and spectrum as the substance.

What plants actually absorb

Spectrum matters because plant pigments are selective. They do not use the whole rainbow equally.

The chlorophyll and carotenoid peaks

The dominant photosynthetic pigments, chlorophyll a and chlorophyll b, absorb most strongly at the blue and red ends of the visible range. Chlorophyll a peaks near 430 nm (blue-violet) and 662 nm (red); chlorophyll b peaks near 453 nm (blue) and 642 nm (orange-red) (Plants in Action / rseco.org). Carotenoid accessory pigments absorb around 450–475 nm, filling in the blue-green region and widening the band of usable light (Alpha Measure).

Green light, between roughly 500 and 580 nm, is largely reflected rather than absorbed, which is precisely why leaves look green to you. That reflection is not pure waste; some green penetrates deeper into the canopy and into lower leaves, and it makes a tank look natural. But the heavy lifting of photosynthesis happens in red and blue.

Red does the most work per photon

Across the action spectrum, red light in the 600–625 nm band is the most efficient at driving photosynthesis, requiring roughly 10 photons per CO2 molecule assimilated versus about 12 at the blue peak near 450 nm (Plants in Action / rseco.org). This is why plant-tuned spectra lean red-heavy. A commonly cited freshwater target is roughly 50% or more red (630–700 nm), about 35% green (500–580 nm) for penetration and natural rendering, and no more than about 15% blue (435–495 nm), since excess blue is associated with algae and a washed-out look (aquariumlesson).

The practical reading: a good planted spectrum is red-forward, with restrained blue and enough green to look right and reach lower leaves. The exact ratios are not gospel, because PAR and PUR (the usable fraction of PAR) move the goalposts, but the direction is consistent across sources.

How LEDs build white light: phosphor white vs RGB vs WRGB

To choose a fixture intelligently, you need to know how its white is made, because the construction method determines both the spectrum and the colour rendering.

Phosphor-converted “white” LEDs

A standard white LED is a blue chip coated with a yellow phosphor; the blue excites the phosphor, and the combined output reads as white. These are efficient and cheap, and they were the backbone of planted lighting for years. The downside is a spectrum with a strong blue spike and a phosphor-driven hump that can be thin in deep red. They grow plants and are inexpensive, which is why white-only panels are now the budget tier.

RGB: white by additive mixing

An RGB fixture has discrete red, green, and blue emitters and makes “white” by mixing them. This gives enormous colour flexibility, since adjusting the three channels produces a vast range of hues. But pure RGB white carries energy only in three narrow bands, with large spectral gaps between the red, green, and blue peaks. Objects whose reflectance falls in those gaps appear shifted or muted, and RGB-mixed white can post a low Colour Rendering Index, typically in the 20–40 range, against the 80–97+ of good phosphor or full-spectrum sources (Lumicrest). The most visible casualty is deep red (the R9 component), which governs how warm-coloured materials, and red plants, render. Pure RGB is great for tunability and poor for honest colour.

WRGB and RGB+UVA: the best of both

The fixtures most aquascapers actually buy combine a white base with discrete red, green, and blue channels (WRGB), or build on RGB with an added white-rendering approach plus an ultraviolet/violet (UVA) channel. The white base fills in the spectral gaps for natural rendering and broad coverage; the discrete R, G, and B channels let the maker, and with an app the user, tune the mix toward what plants use and toward the colours that make fish and red stems pop. Compared with a flat white panel, a good WRGB or RGB+UVA fixture delivers more usable spectrum per watt and far better colour rendering. That second point sells tanks: a red Rotala reads crimson under a quality multi-channel fixture and brown-green under cool white.

What WEEK AQUA tunable LEDs actually do

WEEK AQUA is a specialist aquarium-LED manufacturer with over a decade of focus on planted-tank lighting, and its higher series are built specifically around a tunable, full-spectrum approach. Stripping away the marketing, here is what the hardware does and why it matters.

The spectrum: RGB plus a UVA (violet) channel

WEEK AQUA’s P Series is an RGB light with an added UVA channel. The manufacturer describes it as an RGB+UVA fixture, with the UVA (“black light”) channel intended to lift the brilliance of ornamental fish and the appearance of aquatic plants, echoing the violet end that older T5 fluorescent setups were valued for (WEEK AQUA). Retail listings for the current V3/PRO generation describe it as a full-spectrum WRGB plus ~405 nm UV design, with the high-CRI variants marketed for true colour rendering and a stable spectrum (Aquatic Motiv; The Aquascape Shop). The practical effect of adding violet/UVA on top of RGB is deeper plant coloration and fluorescence in certain fish, the visual refinement that hardscape-and-colour aquascapes are built around. It is a refinement, not a requirement: a function-first planted tank grows perfectly well without the UVA channel.

Per-channel tuning via the app

The defining feature of a tunable fixture is that you control the colour mix yourself. WEEK AQUA’s P Series runs on Bluetooth app control, letting you set brightness, adjust the spectrum balance across channels, and build daily schedules (WEEK AQUA; The Aquascape Shop). This is what makes spectrum a control rather than a one-time purchase decision. You can dial red and white up to favour plant growth and red-plant coloration, hold blue back to discourage algae and avoid a washed-out look, and lift the UVA channel when you want maximum colour pop for viewing or photography.

Sunrise, sunset, and multi-segment scheduling

The current P Series generation supports gradual sunrise and sunset ramps with custom waveforms and an increased number of programmable time schedules, so the light can run multiple intensity-and-spectrum segments across the day for 24-hour automation (WEEK AQUA; The Aquascape Shop). Ramping matters for more than aesthetics: a gradual rise and fall reduces the shock of a hard on/off, and the ability to schedule a peak window lets you align maximum output with a CO2-injection window. How you set the daily on-time, and why a controlled photoperiod is itself an algae lever, is covered in our photoperiod and algae-control guide.

Power, build, and the honest caveats

The P Series PRO scales by tank size: roughly 90 W for 60–80 cm tanks, 135 W for 90–120 cm, and 180 W for 120–150 cm, running on 36 V DC with active fan cooling that holds the surface temperature to around 50 °C or less even at 100% output (The Aquascape Shop; WEEK AQUA). The manufacturer’s own light-quantity guidance is to start positive (demanding) aquatic plants at around 50% output and tune up from there (WEEK AQUA), which is the right instinct: a strong tunable light run too hard, too soon, on a tank that lacks the CO2 and fertiliser to match, feeds algae rather than plants. The fan needs periodic cleaning and the fixture is not for dusty or outdoor use (WEEK AQUA). Full electrical specs, model dimensions, and current-stock SKUs for the Egyptian market are confirmed per order; we can provide them on request.

Where a tunable fixture earns its premium

Spectrum tuning helps only if it gets used. Recommend a tunable WEEK AQUA fixture when the customer cares about plant colour and is willing to touch the app, when the tank is high-tech and benefits from ramping aligned to a CO2 window, or when spectrum needs to become an active algae and coloration control. For a hands-off owner who will leave it on defaults, the tunability is wasted spend, and a simpler fixture on a plug timer is the honest recommendation. Match the fixture to the keeper, not the feature list.

Spectrum as an algae and coloration lever

Because the colour mix is adjustable on RGB-capable fixtures, spectrum becomes a tool you actively use, not just a look you accept.

Pulling blue back to favour plants

Excess blue is associated with algae and a washed-out appearance, while red drives growth and red-plant coloration (aquariumlesson). Aquarists managing problem tanks commonly dial blue down and bring red and white up, shifting the competitive balance toward plants. On a fixed white panel you cannot do this; the factory mix is what you get. On a tunable fixture it is a few seconds in the app. That flexibility is the core practical case for paying up from a fixed panel to an RGB, WRGB, or RGB+UVA unit, before colour rendering even enters the conversation.

Tuning for colour, honestly

Pushing red and violet/UVA makes red stems and certain fish far more vivid, which is the single biggest visual upgrade a multi-channel fixture delivers. Be straight with customers about the trade-off, though: a heavily red-and-violet “show” spectrum can look unnatural for everyday viewing, and the most flattering setting for photographs is not always the most pleasant to live with. The right answer is usually a balanced daily spectrum with the option to push colour for viewing or photography, not a permanently saturated mix.

How Innovote sources this

Innovote Global is the appointed channel for the brands we carry, which is the part of a lighting purchase that does not show up on a spectrum chart but decides whether the fixture is still working in two years.

• Authentic, supported product. We are the exclusive agent for WEEK AQUA in the Egypt territory, so a WEEK AQUA fixture sourced through us is genuine, not a grey-market clone with no warranty path once it crosses the border. The same applies to the wider rig: we are the official distributor for SUNSUN and for YEE.
• Spare parts and after-sales kept local. A tunable fixture is a piece of electronics with a driver, a Bluetooth board, and a cooling fan. WEEK AQUA’s own documentation notes that boards and parts are serviceable, and we keep the spare-parts and warranty path inside Egypt rather than abandoning it at the port.
• Specs on request, confirmed per order. Exact model dimensions, electrical ratings, channel counts, and current-stock SKUs are confirmed per order against the manufacturer’s data; we do not publish a spec we cannot stand behind, and we will send the manufacturer datasheet for any model on request.
• One importer who clears its own goods. The same NAFEZA / ACID / GOEIC import competence behind our industrial lines lands this equipment cleanly, so stock for our 30+ pet-shop network and our online channels arrives predictably.
• Two channels, one product. We supply wholesale to pet shops and aquarium retailers, and direct to hobbyists online on Amazon.com and Amazon Egypt, so the same authentic fixture reaches both the shelf and the home tank.

We do not claim any regulatory “approval” or “certification” for a fixture beyond what the manufacturer documents; capability and compliance evidence is available on request.

Frequently asked questions

Does the Kelvin rating tell me if a light is good for plants?
No. Kelvin only describes how warm or cool the white looks. Two lights at the same 6500 K can have very different spectra and grow plants differently, because growth depends on usable spectral output, not the colour-temperature label (2Hr Aquarist). Use Kelvin to pick the look you like; judge growth on spectrum and PAR.

What colour temperature looks best in a planted tank?
Around 6500 K reads as natural daylight and is the common default, and the broader 6000–8000 K range gives a pleasant output that shows plants well (Aquarium Gardens). On a tunable RGB or WRGB fixture you can shift the apparent colour warmer or cooler without much changing plant performance, so choose the look and let the channels handle the rest.

Is RGB or WRGB better for a planted tank?
WRGB (or RGB+UVA) is usually the better buy. Pure RGB is highly tunable but renders colour poorly, with a CRI often in the 20–40 range because its white has large spectral gaps (Lumicrest). Adding a white base fills those gaps for natural rendering while keeping the per-channel tuning, which is why WRGB and RGB+UVA fixtures dominate the planted-tank market.

What does the UVA channel on a WEEK AQUA P Series actually do?
The UVA (“black light”) channel sits below visible violet and is there to deepen plant coloration and make certain fish fluoresce, echoing the violet end that T5 fluorescent setups were valued for (WEEK AQUA). It is a colour-and-fluorescence refinement for show aquascapes, not a growth requirement; a planted tank grows fine without it.

Can I use spectrum to fight algae?
To a degree, yes. Excess blue is associated with algae, so pulling blue back and favouring red and white shifts the balance toward plants, and on a tunable fixture that is a quick adjustment (aquariumlesson). Spectrum is one lever among several; pair it with a sensible photoperiod and balanced CO2 and nutrients rather than treating it as a standalone cure.

Why does my red plant look brown under one light and red under another?
Colour rendering. A light with spectral gaps in the deep red, common in pure-RGB white, cannot reflect a plant’s red faithfully, so it reads muted or brown (Lumicrest). A high-CRI WRGB or RGB+UVA fixture with strong, complete red output renders that same plant as the crimson it actually is.

Do I need the app, or can I just plug it in?
You can run a WEEK AQUA P Series on a fixed setting, but the app is where its value lives: per-channel spectrum tuning, sunrise/sunset ramps, and multi-segment scheduling (WEEK AQUA). If a customer will never open the app, the tunability is wasted spend and a simpler fixture on a plug timer is the honest call.

Related articles

• How to choose aquarium LED light intensity (PAR) for a planted tank
• Photoperiod and algae control: light scheduling for a balanced planted tank
• Aquascaping & aquarium equipment sourcing: hardware, live plants and aquasoil
• SUNSUN, WEEK AQUA and YEE compared: what each brand is for in your range

Talk to the trade desk

Innovote Global supplies aquascaping equipment, including planted-tank lighting from WEEK AQUA, to retailers and aquascapers across Egypt. If you are speccing fixtures for a build or stocking a range, tell us the tank and the look you want, and our team will match spectrum, channel set, and footprint to the tanks you actually keep. Request a wholesale quote or model spec sheet, and we will come back with model, MOQ, lead time, and a landed-cost path.

Byline: Innovote Trade Desk