10 gallon
20¼ in long and 12 9/16 in tall outside, so plants on 2 in of substrate sit about 10.5 in below a light on the rim. The 10 gallon page
| Light | At the plants, 10.5 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 22W Brackets span 15–24 in · try another depth | At least 110 PAR | High light |
| Fluval Plant 3.0 22W Brackets span 15–24 in · try another depth | At least 80 PAR | High light |
20 gallon long
30¼ in long and 12¾ in tall outside, so plants on 2 in of substrate sit about 11 in below a light on the rim. The 20 gallon long page
| Light | At the plants, 11 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 32W Brackets span 23–35 in · try another depth | At least 120 PAR | High light |
| Fluval Plant 3.0 32W Brackets span 24–34 in · try another depth | At least 107 PAR | High light |
29 gallon
30¼ in long and 18¾ in tall outside, so plants on 2 in of substrate sit about 17 in below a light on the rim. The 29 gallon page
| Light | At the plants, 17 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 32W Brackets span 23–35 in · try another depth | At least 70 PAR | High light |
| Fluval Plant 3.0 32W Brackets span 24–34 in · try another depth | Under 107 PAR Fluval publishes no figure deeper than 12 in for this light. At 12 in it gives 107 PAR, so plants 17 in down get less, and we can’t say how much. The Plant 4.0 lights have figures down to 18 in. | Not published this deep |
30 gallon
36¼ in long and 16¾ in tall outside, so plants on 2 in of substrate sit about 15 in below a light on the rim. The 30 gallon page
| Light | At the plants, 15 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 46W Brackets span 35–49 in · try another depth | At least 80 PAR | High light |
| Fluval Plant 3.0 46W Brackets span 36–46 in · try another depth | Under 112 PAR Fluval publishes no figure deeper than 12 in for this light. At 12 in it gives 112 PAR, so plants 15 in down get less, and we can’t say how much. The Plant 4.0 lights have figures down to 18 in. | Not published this deep |
40 gallon breeder
36 3/16 in long and 16 15/16 in tall outside, so plants on 2 in of substrate sit about 15 in below a light on the rim. The 40 gallon breeder page
| Light | At the plants, 15 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 46W Brackets span 35–49 in · try another depth | At least 80 PAR | High light |
| Fluval Plant 3.0 46W Brackets span 36–46 in · try another depth | Under 112 PAR Fluval publishes no figure deeper than 12 in for this light. At 12 in it gives 112 PAR, so plants 15 in down get less, and we can’t say how much. The Plant 4.0 lights have figures down to 18 in. | Not published this deep |
55 gallon
48¼ in long and 21 in tall outside, so plants on 2 in of substrate sit about 19 in below a light on the rim. The 55 gallon page
| Light | At the plants, 19 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 59W Brackets span 46¼–61 in · try another depth | Under 90 PAR Fluval publishes no figure deeper than 18 in for this light. At 18 in it gives 90 PAR, so plants 19 in down get less, and we can’t say how much. | Not published this deep |
| Fluval Plant 4.0 46W Brackets span 35–49 in · try another depth | Under 80 PAR Fluval publishes no figure deeper than 18 in for this light. At 18 in it gives 80 PAR, so plants 19 in down get less, and we can’t say how much. | Not published this deep |
| Fluval Plant 3.0 59W Brackets span 48–60 in · try another depth | Under 136 PAR Fluval publishes no figure deeper than 12 in for this light. At 12 in it gives 136 PAR, so plants 19 in down get less, and we can’t say how much. The Plant 4.0 lights have figures down to 18 in. | Not published this deep |
On 3 in of substrate the plants sit 18 in down, where Fluval gives 90 PAR for the Plant 4.0 59W and 80 PAR for the Plant 4.0 46W: high light.
75 gallon
48½ in long and 21⅛ in tall outside, so plants on 2 in of substrate sit about 19 in below a light on the rim. The 75 gallon page
| Light | At the plants, 19 in down | Light level |
|---|---|---|
| Fluval Plant 4.0 59W Brackets span 46¼–61 in · try another depth | Under 90 PAR Fluval publishes no figure deeper than 18 in for this light. At 18 in it gives 90 PAR, so plants 19 in down get less, and we can’t say how much. | Not published this deep |
| Fluval Plant 4.0 46W Brackets span 35–49 in · try another depth | Under 80 PAR Fluval publishes no figure deeper than 18 in for this light. At 18 in it gives 80 PAR, so plants 19 in down get less, and we can’t say how much. | Not published this deep |
| Fluval Plant 3.0 59W Brackets span 48–60 in · try another depth | Under 136 PAR Fluval publishes no figure deeper than 12 in for this light. At 12 in it gives 136 PAR, so plants 19 in down get less, and we can’t say how much. The Plant 4.0 lights have figures down to 18 in. | Not published this deep |
On 3 in of substrate the plants sit 18 in down, where Fluval gives 90 PAR for the Plant 4.0 59W and 80 PAR for the Plant 4.0 46W: high light.
125 gallon
72½ in long and 23⅛ in tall outside, so plants on 2 in of substrate sit about 21 in below a light on the rim. The 125 gallon page
No Fluval Plant light spans a tank 72½ in long: the longest brackets reach 61 in.
What the light levels grow
- Low light: Enough for the low-light plants without CO₂. Stem plants and carpets stretch toward the light and fade.
- Medium light: Enough for most stem plants, swords and lilies, and for carpets such as Monte Carlo, which grow thicker with CO₂.
- High light: Enough for carpets and red stem plants. At this level plants need CO₂ and regular fertilizer to keep up; without them, turn the light down in the Fluval app or shorten the day, or algae takes the spare light.
The levels are the ones Aquarium Co-Op prints on its Easy Green label. Plants near the glass get less light than those straight under the fixture.
Before you choose
A light rated for more than your plants need is not wasted: the Fluval Plant lights dim in the Fluval app, and a shorter day keeps algae down while a new tank settles. Measure the tank’s outside length before you order: the brackets must reach both ends of the rim. Aqueon Planted Aquarium Clip-On LED, Finnex Planted+ 24/7 CRV-24, Finnex Planted+ 24/7 CRV-36 and hygger’s 957 Planted Aquarium Light (20 W, 26 W, 36 W, 48 W, 60 W and 72 W) are not ranked here: their makers publish no PAR at depth.
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