The best light for aquarium plants is a combination of the right spectrum and brightness.

This may be slightly different to the stock lights supplied in your aquarium package so many planted tank owners and aquascapers swap their lights out for those with dedicated plant spectrums.

Planted tank light spectrum

The colour of light is measured in something called Kelvin, and most planted aquarium lighting have a Kelvin rating between 6500 and 9000, with 6500K having a yellower hue and 9000K having a whiter hue. Plants actually enjoy the red spectrum of aquarium lighting, right down to about 3000K, but this doesn’t make the aquarium look very aesthetically pleasing so most plant growers use either a single lamp or several lamps with RGB (red, green, blue) in their light spectrum to both enhance plant growth and bring out the rich reds of fish and plants to the human eye. 

Lighting fixtures

Plant growers tend to use either fluorescent light tubes or LED aquarium lighting for plant growth. Fluorescent has been used for decades to grow plants and if you provide plant spectrum tubes and enough of them for the depth of planted tank, plant growth should be enhanced. Reflectors can be used for increased light output down into the tank and T5 tubes are the brightest available. If using multiple T5 a combination of plant, natural daylight, cool white and colour enhancing bulbs can be used to achieve the best overall look and colour in the planted tank 

LED aquarium lights are also available in tube form to mimic and even fit into T5 lamp holders, in the planted aquarium, again available in several spectrums to encourage plant growth, give a clean, white look, or enhance colours. Opt for an open-topped tank and high powered LEDs can be mounted to the tank rim to provide very bright LED light for plants that require it.

Some LED light uses fan cooling (so don’t drop them in the water,) but have the advantage of app control and colour, brightness and duration that is programmed by the planted aquarium owner. This enables a perfect balance of spectrum and output and can even fade in and out to simulate dawn and dusk over lush planted tanks. 

Fertilise your plants for better growth

Healthy aquatic plant growth is not all about light, however, as plants also need plant food to fuel growth. If you increase the lighting in planted tanks but not increase the amount of plant food your plants may become leggy, weak and succumb to opportunistic algae, which also enjoys bright light. Not all plants require bright light either, with Anubias from West Africa naturally inhabiting shaded forests. 

And if you want the ultimate in plant growth complete the triangle of light and nutrients with Carbon Dioxide, which plants use to build their structures. Use a combination of the best LED lights, fertiliser and CO2 for the ultimate in plant growth in your aquarium. 

While you're thinking about your aquarium's decor and plants, you might want to stock up on planted aquarium treatments. Why not try our brand-new Swell Planted range including Swell Planted Aquarium Nitrogen, Swell Planted Aquarium Phosphorus, Swell Planted Aquarium Potassium, Swell Planted Aquarium Booster, Swell Planted Aquarium Iron, Swell Planted Aquarium Carbon and Swell Planted Aquarium Root Tabs.