Aquarium lighting: sizing, mounting and what it will not do
An aquarium light lives directly above water, inside a hood that traps heat and humidity, and it is switched on for hours a day next to livestock that cannot tolerate the wrong spectrum running too long. That is a more specific brief than most lighting jobs, and most of what goes wrong traces back to one of those three things rather than the light itself.
What this category actually is
Our aquarium controllers run on Lotus Lantern — the same app as our other single-colour and tunable-white fixtures. That is worth being upfront about, because a lot of aquarium lighting sold under other brands is RGB, cycling through colour for visual effect, and customers sometimes expect that and are disappointed. What we build is a display and viewing light: white output, adjustable colour temperature on the tunable models, adjustable brightness. It is built to make the tank look right, not to put on a light show.
It is also not a specialist grow light. Planted tanks and reef tanks have real, demanding lighting requirements — specific PAR at the substrate, actinic spectrum for coral — and dedicated horticultural and reef fixtures exist for exactly that. Ours will keep low-light plants alive and will light a reef tank for viewing, but if your tank is built around high-light coral or a carpet plant, you want a fixture designed for that job, not a general display light. We would rather tell you that than sell you the wrong thing.
Sizing to the tank
Buy to the length of the hood or the rim, not the tank's marketed size. A "four-foot tank" can have a hood opening anywhere from about 110 to 122 cm depending on frame style, and the light has to span that opening evenly — a unit sized to the water's edge rather than the actual rim leaves a dark band at one end that is obvious every time you look at the tank from the front rather than from directly above.
For rimless tanks, mount on a clip-on bracket that spans the glass thickness rather than an adhesive pad. Glass thickness varies by tank size, and clip brackets are adjustable; adhesive mounted to glass that later gets cleaned with an ammonia-based glass cleaner will let go, usually onto the substrate.
Where the electronics actually need protecting
This fixture is not designed to be submerged. It mounts above the waterline, on the rim or inside the hood. Low-voltage DC is safer than mains around water but it is not zero-risk, and a fixture rated for splash above the surface is a different product from one rated for submersion. Never rely on a rim-mounted light's rating to justify putting it, or its driver, in the water.
The real hazard on a display tank is not splashing — it is condensation. A glass or acrylic hood traps warm, humid air directly under the fixture, and the driver and connector are the coolest metal surfaces in that space, which is exactly where water vapour condenses first. Two things prevent it from becoming a fault:
- Keep the driver outside the hood if the design allows it — on a shelf below the tank rather than sealed into the humid air above the water.
- Route the cable so it drips away from the connector, not toward it. A cable that runs downhill into the connector carries condensation straight to the one joint that must stay dry.
The electrical code most installers do not know
In the US, NEC Section 210.8(B)(13) requires GFCI (ground-fault) protection for any receptacle within 6 feet of the top inside edge of an aquarium, bait well, or similar open water vessel — the rule exists specifically because aquarium equipment is mains-powered gear kept permanently close to standing water, which is exactly the scenario ground-fault protection is designed for. This applies to the wall receptacle the driver plugs into, not to the low-voltage side of our fixtures, but it matters for the same installation: if the outlet the driver uses is not already GFCI-protected, that is worth fixing before worrying about anything on the fixture side, since it protects every appliance on that circuit, not only the light. A GFCI outlet or breaker is a small, common retrofit, and an aquarium stand is one of the more justified places in a house to have one even where it is not strictly required by the room it is in.
Beyond the code minimum, a drip loop is the practical habit worth forming regardless of what any inspector requires: let the cable hang lower between the fixture and the wall than the outlet itself before it rises to the plug, so any water that does track down the cable drips off at the low point instead of running into the receptacle. It costs nothing and takes seconds, and it is the single most common thing missing from aquarium installs we are asked to look at after the fact.
Why spectrum affects how fish and plants actually look
Colour rendering index matters more on a display tank than almost anywhere else in the house, because the whole point of the fixture is how accurately it lets you see colour — fish pigmentation, coral fluorescence and plant leaf colour all shift under a light with poor CRI, in ways that are obvious side by side but easy to miss if you have never seen the same tank under a better light. A tunable-white fixture set too warm can mute blues and make a tank look slightly yellow overall; set too cool, it can wash out warm reds and oranges on fish and plants that rely on them for their best colour. There is no single correct colour temperature that suits every livestock combination, which is why the adjustment lives in the app rather than being fixed at the factory — the right setting is the one that makes your specific fish and plants look the way they do in good aquarium-shop lighting, and that is worth tuning once by eye rather than trusting a default.
Photoperiod matters more than brightness
Algae growth on a display tank is driven far more by how long the light runs each day than by how bright it is. A consistent 6–8 hour photoperiod, set once on a timer or in the app and left alone, is the single biggest lever against green water and glass algae — more than any amount of cleaning. The mistake we see most often is a light left on all day "so the tank looks nice when people are home", which is also exactly the condition that feeds an algae bloom within a couple of weeks.
Set the schedule in the app once, at a time that matches when you are actually in the room to enjoy it, and stop adjusting it. Consistency is what prevents the bloom; the exact hours you pick matter far less.
Common questions
Can I get this in colour-changing RGB?
Not in this category — it is single-colour or tunable white, built for display rather than effects. If you want colour-changing accent lighting near the tank, that is a different product line; do not run it inside the hood.
Will it grow plants or coral?
It will sustain low-light plants and light a reef tank for viewing. It is not a substitute for a dedicated horticultural or reef fixture if your tank depends on high light levels.
Can I leave it on all day?
You can, but expect algae. A fixed 6–8 hour photoperiod is the better default for almost every tank.
Does the driver need to be on a GFCI outlet?
In the US, code requires it for any receptacle within 6 feet of the tank's rim (NEC 210.8(B)(13)). Outside that distance or outside the US, it is not always mandated, but it remains good practice near any open water vessel — check your local wiring rules if you are unsure.
My tank looks slightly yellow even on a "cool" setting
Check the photoperiod schedule is not running at a lower brightness scene than you think, and confirm the fixture is a tunable-white model rather than fixed colour temperature — some early single-temperature units are warmer by design and are not adjustable in the app the way the tunable range is.
Which app runs this?
Lotus Lantern. Full mapping here if you are not sure which fixture you have.
Contact us if you want a length checked against your hood before you order.