Best Planted Tank Lights for 20-Gallon Aquariums (2026)
Plant lights matched to the 24-inch 20 high and the 30-inch 20 long, with notes on why the deeper 20 high and 29 need more output.
"20 gallon" covers two common shapes, so start with length. For a 20 high (commonly about 24 inches long), the Fluval Plant 3.0 22 W, Fluval Plant 3.0 32 W, and Finnex Planted+ 3.0 24 in are all listed to fit, though 24 inches sits at the edge of each Fluval range. For a 20 long (commonly about 30 inches), the Fluval Plant 3.0 32 W fits mid-range, the Finnex Planted+ 3.0 24 in reaches it at full extension, and the general-purpose Finnex Stingray 3.0 30 in suits low-tech plantings. Pick the Fluval for app scheduling and the Finnex lights for a built-in timer with no app.
Who this guide is for
This guide is for keepers lighting a 20-gallon planted tank. The two shapes sold under that volume behave very differently under a light:
| Tank | Common dimensions (L x W x H) | What it means for lighting |
|---|---|---|
| 20 gallon high | 24 x 12 x 16 in | Shorter fixture, but deeper water |
| 20 gallon long | 30 x 12 x 12 in | Longer fixture, shallow water |
| 29 gallon | 30 x 12 x 18 in | Same length as a 20 long, much deeper |
These are common dimensions, not a standard. Brands vary by an inch or more, so measure your own tank's length and water depth before ordering.
Depth is the part people miss. A 20 high is about 4 inches taller than a 20 long, and a 29 is about 6 inches taller, even though the 29 takes the same 30-inch light as a 20 long. Tropica notes that the amount of light decreases considerably with the distance from the light source to the base of the tank. A light that grows a carpet in a shallow 20 long may be noticeably weaker at the substrate of a 20 high or a 29. For the deeper tanks, favor a fixture with more output and dim it down if needed.
The picks suit low-tech tanks and tanks with injected CO2. If you have not chosen yet, see our low-tech vs high-tech guide.
Quick comparison
| Product | Fits | Best for | Skip if |
|---|---|---|---|
 Fluval Plant 3.0 Bluetooth LED (22 W / 15-24 in (38-61 cm))Model 14520 | 15–24 in long | Planted tanks about 15-24 in long where you want app-programmed sunrise/sunset scheduling. | You want a light you can schedule without a smartphone app, or your tank length falls outside the bracket range. |
 Fluval Plant 3.0 Bluetooth LED (32 W / 24-34 in (61-85 cm))Model 14521 | 24–34 in long | Planted tanks about 24-34 in long where you want app-programmed sunrise/sunset scheduling. | You want a light you can schedule without a smartphone app, or your tank length falls outside the bracket range. |
 Finnex Planted+ 3.0 (24 in)Model PL-24S | 24–30 in long | Planted tanks about 24-30 in long where you want a simple built-in timer and dimmer with no app. | You want app control or custom color-channel scheduling. |
 Finnex Stingray 3.0 (30 in)Model VL-30S | 30–39.5 in long | Low- to moderate-light planted tanks about 30-39.5 in long where you want a simple built-in timer and dimmer. | You plan demanding high-light plants or a deep tank, or you want app control. |
The picks
Fluval Plant 3.0 22 W (15-24 in): for a 20 high only
Fluval Plant 3.0 Bluetooth LED (22 W / 15-24 in (38-61 cm))
- Best for
- Planted tanks about 15-24 in long where you want app-programmed sunrise/sunset scheduling.
- Skip this if
- You want a light you can schedule without a smartphone app, or your tank length falls outside the bracket range.
- Fits tanks
- 15-24 in (38-61 cm)
- Power
- 22 W
- Luminous flux
- 1450 lm
- Number of LEDs
- 99
- Input / operating voltage
- 100-240 V / 24 V
- Control
- Illuminated touch switch (off, all on, blue only, Bluetooth mode) with manual dimming; FluvalSmart Bluetooth app for 24-hour programmed cycle
- Mounting
- Extendable mounting brackets, placed on the outside of the aquarium frame; glass thickness 3-15 mm
- Rated LED life
- 50,000 hours
- Warranty
- 3-year limited
- Extendable brackets cover a 15-24 in tank-length range per the manual
- Programmable 24-hour light cycle via the FluvalSmart Bluetooth app
- 3-year limited warranty
- Programming a schedule requires a phone with the FluvalSmart app
- Dimming level set at the touch switch stays fixed until changed manually
- LED light source is not replaceable
Exact model: Fluval Plant 3.0 Bluetooth LED, model 14520, 22 W, for tanks 15 to 24 inches. It does not fit a 30-inch 20 long.
Fit: On a 24-inch 20 high, the brackets are at the top of their 15 to 24 inch range, so confirm your tank's outside length first. The brackets sit on the outside of the frame on glass 3 to 15 mm thick, per the manual.
Output and controls: A plant-specific light rated at 22 W and 1,450 lumens. It is the lowest-output pick here, which matters on the deeper 20 high; it suits easy and moderate plants better than a high-light carpet. Manual dimming is at the touch switch; a programmed 24-hour cycle needs the FluvalSmart app over Bluetooth.
Maintenance: Keep the fixture dry and wipe condensation off during water changes. The LED source is not replaceable; Fluval lists a 3-year limited warranty.
Fluval Plant 3.0 32 W (24-34 in): for a 20 long, 29, or 20 high
Fluval Plant 3.0 Bluetooth LED (32 W / 24-34 in (61-85 cm))
- Best for
- Planted tanks about 24-34 in long where you want app-programmed sunrise/sunset scheduling.
- Skip this if
- You want a light you can schedule without a smartphone app, or your tank length falls outside the bracket range.
- Fits tanks
- 24-34 in (61-85 cm)
- Power
- 32 W
- Luminous flux
- 2350 lm
- Number of LEDs
- 168
- Input / operating voltage
- 100-240 V / 24 V
- Control
- Illuminated touch switch (off, all on, blue only, Bluetooth mode) with manual dimming; FluvalSmart Bluetooth app for 24-hour programmed cycle
- Mounting
- Extendable mounting brackets, placed on the outside of the aquarium frame; glass thickness 3-15 mm
- Rated LED life
- 50,000 hours
- Warranty
- 3-year limited
- Extendable brackets cover a 24-34 in tank-length range per the manual
- Programmable 24-hour light cycle via the FluvalSmart Bluetooth app
- 3-year limited warranty
- Programming a schedule requires a phone with the FluvalSmart app
- Dimming level set at the touch switch stays fixed until changed manually
- LED light source is not replaceable
Exact model: Fluval Plant 3.0 Bluetooth LED, model 14521, 32 W, for tanks 24 to 34 inches (61 to 85 cm).
Fit: A 30-inch 20 long or 29 sits in the middle of the bracket range. A 24-inch 20 high is at the bottom edge, so measure carefully. Mounting and glass-thickness limits match the 22 W model.
Output and controls: Fluval lists 32 W, 2,350 lumens, and 168 LEDs, noticeably more than the 22 W version, which gives headroom for the deeper 29 and 20 high. Scheduling works through the FluvalSmart app; the touch switch handles on/off, blue only, and manual dimming.
Maintenance: As above. Start a new tank at reduced intensity and raise it as plants establish.
Finnex Planted+ 3.0 (24 in): for a 20 high or 20 long
Finnex Planted+ 3.0 (24 in)
- Best for
- Planted tanks about 24-30 in long where you want a simple built-in timer and dimmer with no app.
- Skip this if
- You want app control or custom color-channel scheduling.
- Fixture length
- 23.50 in
- Max length with mounts extended
- 33.50 in
- Fixture width x height
- 2.34 x 1.30 in
- Power
- 30 W
- PAR at 12 in
- 115 umol/m2/s
- PAR at 18 in
- 60 umol/m2/s
- Spectrum
- Includes 660 nm deep red LEDs; CRI > 92
- Control
- Inline controller: manual dimming 0-100%, daylight/moonlight modes, Auto 24/7 Lunar+ with 6H/9H/12H timer
- Water resistance
- IP67
- Mounting
- Adjustable sliding tank mounts
- Built-in 24/7 Lunar+ timer (6, 9 or 12 hours) without needing an app
- Manufacturer PAR chart lists 115 umol/m2/s at 12 in
- IP67 water-resistance rating
- Timer offers only 6, 9 or 12 hour presets
- No app or per-channel color control
Exact model: Finnex Planted+ 3.0, model PL-24S, 24-inch version.
Fit: The fixture body is 23.50 inches. We treat it as a 24 to 30 inch fit, the narrower of two published figures (Finnex's chart gives 33.50 inches with mounts extended; the retail listing says 30). That covers both 20-gallon shapes, but each sits at one end of the range, so measure. It rests on the rim with sliding mounts; Finnex does not mention a hanging kit.
Output and controls: A plant-specific light. Finnex lists 30 W and PAR of 115 umol/m2/s at 12 inches and 60 at 18 inches, with 660 nm deep red LEDs. The inline controller offers 0 to 100 percent dimming, daylight and moonlight modes, and an automatic 24/7 Lunar+ cycle with 6, 9, or 12 hour presets, no app required.
Maintenance: Finnex rates it IP67. Keep the controller and power supply above and away from the tank, with a drip loop on the cord. For photoperiods other than the presets, add a plug-in timer.
Finnex Stingray 3.0 (30 in): for a low-tech 20 long or 29
Finnex Stingray 3.0 (30 in)
- Best for
- Low- to moderate-light planted tanks about 30-39.5 in long where you want a simple built-in timer and dimmer.
- Skip this if
- You plan demanding high-light plants or a deep tank, or you want app control.
- Fixture length
- 29.49 in
- Max length with mounts extended
- 39.49 in
- Fixture width x height
- 2.34 x 1.30 in
- Input power
- 22 W
- PAR at 6 in
- 140 umol/m2/s
- PAR at 12 in
- 75 umol/m2/s
- PAR at 14 in
- 65 umol/m2/s
- PAR at 18 in
- 52 umol/m2/s
- Spectrum
- Includes 660 nm deep red LEDs; CRI > 92
- Control
- Inline controller: dimming 0-100%, daylight/moonlight modes, Auto 24/7 Lunar+ with 6H/9H/12H timer and adjustable daylight/moonlight intensity
- Water resistance
- PCB IP67
- Power supply
- UL listed
- Rated LED life
- 50,000 hours
- Mounting
- Adjustable sliding tank mounts
- Built-in 24/7 Lunar+ timer (6, 9 or 12 hours) with no app needed
- Manufacturer PAR chart lists 75 umol/m2/s at 12 in
- IP67-rated LED board and 660 nm deep red LEDs
- Timer offers only 6, 9 or 12 hour presets
- No app or per-channel color control
- Modest output for deep tanks (52 umol/m2/s at 18 in per Finnex)
Exact model: Finnex Stingray 3.0, model VL-30S, 30-inch version. It does not fit a 24-inch 20 high.
Fit: The fixture body is 29.49 inches, and the Finnex chart lists 39.49 inches with mounts extended, so it fits tanks from 30 to about 39.5 inches. A 30-inch tank is at the bottom edge; measure the outside length.
Output and controls: This is a general-purpose fixture, not a dedicated plant light. Finnex calls the Stingray 3.0 an all-purpose aquarium LED with lower published PAR than the Planted+ 3.0 line: 75 umol/m2/s at 12 inches and 52 at 18 inches. That fits a shallow, low-tech 20 long with easy plants better than a deep 29 aimed at carpets. Controls match the Planted+ 3.0: dimming, moonlight, and the 6, 9, or 12 hour Lunar+ timer.
Maintenance: PCB rated IP67, UL-listed power supply, 50,000-hour rated LED life per Finnex.
Alternatives and when to skip a new light
- Your 20 high is not 24 inches, or your 20 long is not 30. Rimless and specialty tanks vary. If your length falls outside every range above, do not stretch a fixture to fit; check the lighting hub and our lighting guide.
- Your current light already grows your plants. Adding a timer for a consistent photoperiod may be the better upgrade. See the timers guide.
- You want high light in a deep 29 or 20 high. Budget for CO2 and fertilization alongside the stronger light, or algae tends to win.
How we chose
- Compatibility first. Each light's published length range had to cover the common 24-inch 20 high, the 30-inch 20 long, or both. If Finnex's chart and a retail listing disagreed on fit, we used the shorter range.
- Identity confirmed by matching Amazon's product data to the manufacturer model number.
- Specifications from Fluval and Finnex documentation, listed in the sources.
- A 4-star minimum on Amazon at the time we checked. That screens out poorly rated listings; it does not rank the picks.
- No hands-on testing, no scores. This guide is research-based, and each pick suits a different tank shape and need rather than ranking above the others.
Related guidance
Set your starting intensity and photoperiod with the light intensity and duration guide, and read how to choose planted aquarium lighting for mounting and PAR basics. The setup finder helps match lighting with CO2, filtration, and substrate.
For other tank sizes, see our lights for 10-gallon aquariums and lights for 40-gallon aquariums. Both picks here are compared size by size in Fluval Plant 3.0 vs Finnex Planted+ 3.0, and each has its own write-up: the Fluval Plant 3.0 review and the Finnex Planted+ 3.0 review.
Plant lighting: what to check before you buy ↗Sources
- Fluval Plant Spectrum LED (Plant 3.0) instruction manual, models 14520-14523, Fluval
- FluvalSmart App user manual, Fluval
- Finnex Planted+ 3.0 Aquarium LED Light, Finnex
- Finnex shop: Planted+ 3.0 Series 24, 36, 48 inches, Finnex
- Finnex Stingray 3.0 Aquarium LED product page, Finnex
- Finnex LED Series Comparison Chart, Finnex
- The right light for your aquarium, Tropica Aquarium Plants
This page is research-based: we have not tested the equipment or methods ourselves. It draws on the sources listed and established hobby practice.
Keep reading
How to Choose Planted Aquarium Lighting
Choose a planted tank light by tank length, water depth, mounting style, and the plants you want, not by gallons or watts per gallon.
Aquarium Light Intensity and Duration for Planted Tanks
How bright and how long to run a planted aquarium light: a conservative starting photoperiod, ramping up, siestas, and reading your plants and algae.
Aquarium Timers and Lighting Schedules
How to put your planted tank light and CO2 solenoid on a reliable schedule: timer types, load ratings, power cuts, and step-by-step setup.