Comparing the Chihiros WRGB 2 Slim vs WRGB 2 Pro is not really about which light is better — it is about which tank you own. These two fixtures look nearly identical on the rim of a 60 cm tank, yet the Pro pushes out roughly three times the light of the Slim. Buy the Pro for a low-tech setup and you will not get faster growth. You will get an algae farm.
Both run the My Chihiros app, both are splash-resistant, and both will make a planted tank glow. But they serve opposite jobs: the Slim for low- to mid-tech tanks, the Pro for CO2-injected aquascapes and deep tanks. Here is how to match the light to your tank.
Short answer: Buy the WRGB 2 Slim if your tank has no CO2 injection and the water is shallower than about 45 cm — its 45 W, 2,400-lumen output at 60 cm covers demanding plants in low- to mid-tech setups efficiently. Buy the WRGB 2 Pro if you inject CO2, keep red stems or carpets, or run a tank deeper than 45 cm — its 74 W, 6,630-lumen output holds intensity where the Slim fades. Both are Bluetooth-controlled, splash-resistant, and carry a 2-year warranty.
Output: the real difference
Look at the 60 cm models side by side, from the published spec sheets:
| Feature | WRGB 2 Slim 60 | WRGB 2 Pro 60 |
|---|---|---|
| Power | 45 W | 74 W |
| Luminous flux | 2,400 lm | 6,630 lm |
| LEDs | 40 pcs, RGB 3-in-1 | 60 pcs, WRGB (RGB + white) |
| Body | 584 × 128 × 15 mm | 600 × 140 × 18 mm |
| Light per liter in a 65 L tank | ~37 lm/L (mid-tech) | ~102 lm/L (high-tech) |
| Recommended for | Low- to mid-tech, water under ~40 cm | CO2 tanks, red plants, water over 45 cm |
The ratio holds across the lineup: the Pro 90 runs 110 W / 9,250 lm, firmly in a different output class from anything in the Slim range. Green Aqua's head-to-head puts it bluntly — the Slim is for demanding plants in lower aquariums, the Pro for high-tech aquariums with CO2 injection.
Spectrum and color rendering
The names hide the second difference. The Slim uses RGB 3-in-1 LEDs — red, green and blue diodes in one package, no dedicated white. The Pro is a true WRGB fixture: separate red, green, blue and white LEDs, each independently controllable in the app.
Both render a planted tank beautifully — the RGB-heavy mix is why Chihiros lights are famous for reds. But the Pro's white channel gives a cleaner midday look, and its headroom pushes Alternanthera, Ludwigia and Rotala to deep crimson. In a shallow tank the Slim's color is genuinely excellent — but for a scape built on red stems, the Pro wins.
The CO2 rule (and the algae warning)
A high-output light without CO2 is not a luxury — it is a liability: hair algae, green spot and black beard arrive faster than your plants can photosynthesize. The Slim is far more forgiving at 45 W, sitting in the mid-tech band where liquid carbon, good circulation and consistent water changes keep algae in check — and it still grows demanding plants in a shallow tank.
Design, control and build
The Slim is the prettier object: 15 mm thick against the Pro's 18 mm, a slimmer profile that all but disappears over a rimless tank. Both use adjustable stainless brackets and accept hanging kits and shades. Control is identical — the My Chihiros app over built-in Bluetooth handles sunrise/sunset, dimming, timers and presets, with an optional hub adding Wi-Fi. Both are IP43 splash-resistant and carry a 2-year warranty through your seller, so buy from an established aquascaping retailer rather than the cheapest gray-market listing.
Which one should you buy?
- No CO2, low- to mid-tech plants, water under ~40 cm — buy the Slim. It is the right amount of light, it sips power, and it will not punish a missed water change. Match the model number to your tank length (Slim 60 for 60–80 cm tanks).
- CO2 injection, red stems or carpets, water deeper than 45 cm — buy the Pro. Nothing else in the Chihiros line holds intensity at depth like it, and you will actually use the output you paid for.
- Upgrading from a basic white LED on a CO2 tank — the Pro is the ceiling-raiser; the Slim is a sidegrade in output.
If your setup fits the Pro's profile, the Chihiros WRGB II Pro 60 ★4.1 carries a Best Seller badge on Amazon with a 4.1-star average from aquarist reviews.
Affiliate disclosure: AquaVerdia is reader-supported. If you buy through the Amazon link above, we may earn a commission at no extra cost to you — it helps fund independent guides like this one.
For the Slim, order from a specialty aquascaping retailer — there is no verified live Amazon US listing of the Slim fixture right now (one popular lookalike ASIN is actually just the shade accessory). Check the published Slim 60 spec sheet for exact per-size wattage and dimensions.
Frequently asked questions
Can I use the WRGB 2 Pro without CO2?
Yes, but dim it hard — 50–60% intensity, 6–8 hour photoperiod. Without CO2 you pay for output you cannot safely use, so the Slim is the smarter buy for the same tank.
Is the Slim enough for red plants?
In tanks under about 40 cm deep, yes — Alternanthera, Ludwigia and red Rotala color up well with good fertilization. Past 45 cm of water, the Pro earns its keep.
Do I need the Chihiros Wi-Fi hub?
No. Both fixtures are fully controllable over built-in Bluetooth — schedules, dimming, sunrise/sunset and color channels all work without it. The hub only adds Wi-Fi remote control.
Which is better for a standard 60P low-tech tank?
The Slim 60. Its ~37 lumens per liter sits in the mid-tech band, while the Pro 60's ~102 lm/L would demand CO2 and strict maintenance to stay algae-free.