Planted-tank lighting
Aquarium Light Schedules and Timers
Compare aquarium light schedules including ramps, overlaps and midnight crossings, calculate uninterrupted fixture-off intervals and check timer restart limitations.
Define the light period before choosing the timer
An aquarium timer is useful because it makes a suitable lighting plan repeatable. It cannot decide what that plan should be. Start with the plants and livestock, the aquarium’s stage and any daylight reaching it. Then choose the hours and supported intensity you can operate consistently.
Tropica’s growing-in guidance begins a new planted aquarium at six hours of light daily for the first two to three weeks before gradually increasing. That provides a practical establishment reference; it is not a requirement to keep lengthening every aquarium’s day. A low-tech setup with modest plant demands may need a different balance from a high-output injected-CO₂ layout.
RSPCA advice also emphasises a steady day/night cycle and switching aquarium lighting off at night. A night mode or blue channel is still illumination, so provide a proper dark period. If the aquarium receives direct sun, address its location and shading rather than counting only the LED’s scheduled hours.
Keep duration, brightness and ramps separate
Duration is how long the fixture emits light. Intensity is its output at a particular setting and location. A sunrise ramp changes intensity over time, but it still contributes light exposure. A programme with several hours of dim blue output is not equivalent to darkness simply because the controller calls that slot “night”.
For an illustrative six-hour block, 2pm to 8pm can make viewing possible after work. Those are example clock times, not a recommended schedule for every aquarium. Choose a plan that suits the fish and plants, then observe new growth, algae and the overall aquarium rather than moving the on/off time every day.
Avoid increasing both intensity and duration together when diagnosing poor growth. Nutrients, carbon availability, plant choice and shading can be involved. Our low-tech lighting guide helps you assess the fixture’s role before treating every plant problem as too few hours.
Compare the whole programme, including ramps and viewing modes
A six-hour main-light period can sit inside a much longer illuminated day. We calculated six fictional daily programmes to show the difference. Count every minute when any scheduled channel emits light, including dim ramps and blue viewing periods; count overlapping channels only once when calculating elapsed illuminated time.
These clock times are arithmetic examples, not recommended plant or fish schedules, and they are not claimed to be available on every controller. A ramp interval below is assumed to emit some light throughout its stated interval; exact zero-output endpoints do not add duration at this one-minute resolution.
| Example programme | Any channel emitting | Total fixture-off time | Longest continuous fixture-off interval |
|---|---|---|---|
| One six-hour block Main light 14:00–20:00 | 6 hours | 18 hours | 18 hours |
| Block plus ramps Ramp 13:00–14:00; main 14:00–20:00; ramp 20:00–21:00 | 8 hours | 16 hours | 16 hours |
| Block plus late blue Main 14:00–20:00; blue 20:00–23:00 | 9 hours | 15 hours | 15 hours |
| Two three-hour blocks Main 11:00–14:00 and 17:00–20:00 | 6 hours | 18 hours | 15 hours |
| Six hours across midnight Main 20:00–02:00 | 6 hours | 18 hours | 18 hours |
| Overlapping channels Main 14:00–20:00; blue 19:00–22:00 | 8 hours | 16 hours | 16 hours |
Adding a one-hour ramp before and after the 14:00–20:00 block changes the fixture's emitting time from six to eight hours. Keeping blue output on until 23:00 instead gives nine hours. A controller's “night” name does not make that period dark.
The split example still totals six illuminated hours and eighteen off hours, but the longest uninterrupted off interval is fifteen hours, from 20:00 to 11:00 the next day. Its other three off hours sit between the daytime blocks. Total off time and one continuous off period therefore answer different questions. This comparison does not establish a benefit from split lighting.
Count overlaps once and carry the clock across midnight
In the overlapping-channel example, six main-light hours plus three blue-channel hours contain one shared hour. The elapsed emitting period is eight hours, from 14:00 to 22:00, rather than nine. A block from 20:00 to 02:00 lasts six hours even though its end clock time is numerically smaller than its start.
Our calculation converts clock times to minutes in a 24-hour day, marks minutes covered by any interval and counts that combined set. The longest off interval is measured around the repeating daily cycle, so an interval crossing midnight is kept together. The download includes the input intervals and the derived minute counts.
Download all six programmes and their timing calculations (CSV)
These are fixture-off intervals, not measurements of actual darkness in the aquarium. Sunlight and room lighting can still reach the fish. Likewise, elapsed hours do not measure light dose: controller percentages, ramp shapes, spectrum, shading and PAR at the leaves remain separate. Do not multiply an unverified dimmer percentage by hours and present it as measured plant exposure.
Choose controls that preserve the intended programme
The NICREW C10 manual documents a clock-based programme and a reset to 08:00 after power restoration. The Brennenstuhl DT GB specification documents the timer's own data memory. They describe different devices and cannot be combined into a promise that a light's clock will stay correct.
| Device | Stored data | Clock or connected-light limitation | Practical consequence |
|---|---|---|---|
| NICREW C10 24/7 | Programmes retained | Clock returns to 08:00 after power restoration | Reconfirm current time in 24/7 mode; daily mains switching can reset the clock |
| Brennenstuhl DT GB 1507503 | Manufacturer lists data memory after a power cut | Memory claim does not establish the connected light’s clock or restart state | Check the timer’s own clock and mode, plus the light’s restart instructions |
A mains timer with programme memory cannot restore a separate controller's lost time. Equally, a programmable light does not establish that an external timer suits its power supply. Use the exact manuals for supported time slots, load type and restart behaviour. The six examples above remain planning comparisons until the chosen hardware can implement them.
For care context, Tropica's growing-in guidance and the RSPCA's day/night guidance provide different plant-establishment and livestock considerations. Adapt the actual programme to the aquarium, preserve a suitable night and use plant-level light measurements for questions that timing alone cannot answer.
Use built-in scheduling where it fits the requirement
Some lights have an elapsed-hours timer, some use a real-time programme and others offer a simple brightness controller. Identify what the exact selected model does. A six-hour timer activated at a particular moment may not behave like a clock-based schedule following a power interruption. Read the instructions before relying on it while away.
The NICREW C10 24/7 below uses an infrared remote and time-slot programming. Its manual distinguishes saved settings from the clock: after a power cut, programmes remain but the clock returns to 8am, and the present time needs reconfirming. That makes daily mains switching a different proposition from leaving the controller appropriately powered and using its own programme.
Remote programming on a shorter adjustable bar
NICREW C10 24/7 aquarium light, 43–60 cm
An adjustable freshwater LED bar with an infrared remote and a programmable 24/7 mode. Choose the programme around the plants and a proper dark period rather than leaving every default time slot unchanged.
- 43–60 cm selected mounting range
- 15 W listing variant
- Remote and inline controller
A compatible 43–60 cm mounting span with clear access to the infrared receiver and plants suited to the installed light.
- The manual says programmes survive a power cut but the clock returns to 8am; reconfirm the time.
- A mounting range does not guarantee uniform substrate illumination at every depth.
Fluval Plant 4.0 offers an app-controlled programme, while other fixtures use wired controls or different timer formats. Do not transfer a C10 reset procedure or app assumption to another family. Check the exact controller, present time, selected mode and dark period after setup.
Choose an external timer only for a compatible arrangement
A mains timer switches power; it does not know what the light’s internal controller will do when power returns. A suitable light may resume its intended on-state, while another may reset its clock, choose a default colour or require a button press. A timer that remembers its own programme cannot fix a light that restarts in the wrong mode.
The Brennenstuhl Primera-Line DT GB is a dry indoor digital weekly timer to assess for a compatible lighting load. The manufacturer lists 20 on/off programmes, a one-minute minimum switching step and memory for its own data after a power cut. Check both products’ supplied instructions, including permitted load type and the light’s restart behaviour. We do not claim this timer is universally compatible with every aquarium LED driver.
A dry indoor timer for a compatible light
Brennenstuhl Primera-Line digital weekly timer, DT GB
A UK-format digital weekly timer with programmed on/off events and memory for its own settings. Use it only with a lighting load and power-restoration behaviour supported by both manufacturers.
- UK model 1507503
- 20 on/off programmes; one-minute minimum step
- IP20 indoor-only timer
A compatible mains-powered aquarium light whose controls return to the intended state after the timer restores power.
- Keep dry and outside splash or condensation zones; verify load type as well as wattage against the supplied instructions.
- Timer memory does not guarantee that the light’s own clock or programme resumes correctly.
Keep IP20 indoor timers, plugs and power supplies outside splash and condensation zones. Fit the complete plug securely and follow the cable and electrical arrangement specified by the equipment manufacturers. Do not choose a timer solely from a large headline wattage: load restrictions and the actual lighting power supply also matter.
Leave filtration and thermostatic heating appropriately available. Do not connect the whole aquarium power strip to the light timer, which would shut unrelated essential equipment down every evening. Switch only the intended compatible lighting circuit.
Check an entire on/off cycle before relying on it
- Confirm the selected timer mode and the current clock time.
- Set the intended on and off events for the correct days.
- Remove conflicting programmes and disable random or countdown modes unless deliberately needed.
- Check the light starts in the desired colour and brightness when scheduled power returns.
- Confirm the fixture reaches the intended dark period after the off event.
- Recheck after a power interruption or seasonal clock change, using the exact instructions.
Where a brief power-restoration check is supported by the equipment instructions, perform it during setup and observe the result. Do not repeatedly interrupt the whole aquarium to test a light. A phone reminder may help you inspect the first cycle, but does not replace suitable unattended operation.
A timer accidentally left in manual-on mode can defeat a perfect programme. Likewise, overlapping daily and weekly events can create an unexpected extra light period. Keep the final plan simple enough that you can explain exactly what will happen on an ordinary day.
Adjust the aquarium plan using observations
Record the light model, output setting and actual programme in your care notes. If algae increases or plant growth changes, review the rest of the aquarium as well as the light. Avoid a permanent cycle of extending the day, then making large abrupt reductions without understanding the pattern.
Count the full programme, including ramps and late viewing modes. Keep daytime viewing compatible with a real night rather than adding blue light until bedtime indefinitely. If you need to change the viewing window, move a consistent block within an appropriate routine rather than expanding its total length automatically.
Finally, check fit and light coverage. A schedule cannot make a short bar illuminate a shaded end evenly or correct a badly mounted clip-on light. Appropriate hardware, manageable output and a repeatable programme work together.
For a programme that appears correct but gives poor growth, follow the light-change investigation. Use light measurements to distinguish controller percentages, plant-level intensity and duration.
Before an absence, include the verified programme in holiday preparation. After an interruption, follow device-by-device recovery checks rather than assuming that a restored display has kept its clock.
Common questions
How long should lights run on a new planted aquarium?
Tropica starts its growing-in guidance at six hours daily for the first two to three weeks, then increases gradually. Use that as a starting reference alongside the actual plants and aquarium conditions, rather than automatically choosing the longest available programme.
Does blue moonlight count as darkness?
No. Blue output is still light and contributes to the aquarium’s illumination period. Provide a proper dark interval for the livestock instead of assuming a night label means the fixture should remain visibly lit all night.
Can a mains timer control every aquarium LED?
Compatibility depends on the timer’s load restrictions and the light’s power-restoration behaviour. Some controllers lose their clock, return to a default mode or need manual input. Check both manuals and verify the intended switching cycle before relying on it.
Why is my C10 schedule wrong after a power cut?
The NICREW C10 manual says programmes are retained but the clock returns to 8am when power is restored. Reconfirm the current time in 24/7 mode rather than assuming saved colour settings mean the clock also stayed correct.
Should the filter go on the same timer as the light?
Do not schedule the whole aquarium off with the lighting. Filtration normally needs continuous operation and thermostatic heating needs appropriate ongoing availability. Use a compatible arrangement that switches only the lighting intended for the schedule.
Should I add more hours if the plants grow slowly?
Review plant requirements, shading, output, nutrients and available carbon first. Longer duration does not correct every growth limitation and can worsen an unbalanced setup. Make considered adjustments and observe the result rather than changing several settings together.