Aquarium Lighting Guide: How Much Light for Plants and Fish
By Melbourne Tropical Team ยท 2 min read
Aquarium lighting affects plant growth, fish colour and algae. Here is how to choose the right light and how long to run it - in plain English.
Light for fish-only tanks
If you don't keep live plants, lighting is mostly about seeing and showing off your fish. A modest LED is plenty. Keep it on for a set period each day and avoid leaving it on constantly, which stresses fish and grows algae.
Light for planted tanks
Plants need enough light to photosynthesise, measured by PAR (the useful light reaching the plants) rather than watts. As a rough guide: low-light, easy plants (anubias, java fern, crypts) need modest light; carpeting plants and red stems need strong light - and usually CO2 - to thrive. Match your light to the plants you want, not the other way around. Our lighting calculator helps you judge the level.
How long to run your lights
Most tanks do best with 6-8 hours of light a day, ideally on a timer for consistency. Longer periods rarely help plants and usually just feed algae. If you battle algae, shorten the photoperiod before anything else, and keep the tank out of direct sunlight.
Choosing an LED
LEDs are now the standard - they are efficient, long-lasting and run cool. For plants, choose a unit designed for planted tanks with a full spectrum and enough output for your tank's depth. A built-in timer or a separate plug-in timer makes consistent lighting effortless.