Light plays a vital role in an aquarium, but as they say, “Excess of everything is bad.”

Too much light could very well turn out to be a disaster for your aquarium plants. In this article, we will list the five key signs to look out for to prevent damage from overexposure to light.


1. Overgrown Leaves

You might be happy when you see the leaves of your aquatic plant growing quickly, but when you stop to pay attention, trouble starts brewing.

Overgrown plants increase your maintenance workload significantly as you need to prune them frequently. This becomes even more critical if you have a small tank.

Secondly, your fish could be affected as they will have lesser room to move around. They could very well stress up and show signs such as aggression and poor appetite.

Reducing the amount of lighting your plants get can help control their growth.

2. Leaves Changing Color


An indication that the plants in your aquarium are getting too much light is when their leaves start to change color.

For instance, if the plant used to be in a dark environment and is suddenly moved to a brighter one, it could turn yellow.

The plant could take about a week to return to its original color. Note that this will only happen if you adjust the lighting to its needs.

If the leaves turn purple or red, the light intensity is too high. It causes chlorophyll to break down, which results in the change of color in the leaves.

Lastly, if the leaves turn brown, it could be due to excess heat and burning caused by overexposure to light.

3. Brown Edges On Leaves

Brown edges on the leaves of aquatic plants indicate heat stress due to excessive lighting. It’s as if the edges of the leaves are getting ‘fried.’

4. Algae


The excessive growth of algae in an aquarium tank is caused due to an abundance of light and nutrients.

Many hobbyists believe that keeping their tanks in the dark can prevent the situation, but they couldn’t be more wrong.

The viable solution is to regulate the amount of light the tank receives, change the water regularly, and not overfeed your tank to prevent the buildup of nutrients.

Additionally, adding fish that feed on algae can also help control their growth.

5. Rotting Leaves

This is usually a side effect of algae growth and has no direct relation to light.

Uncontrolled populations of algae (induced by overexposure to light) can cover up the leaves of aquatic plants— choking them of light and nutrients.

This, in turn, can cause the leaves to start rotting.

How Much Light Should Aquatic Plants Get?


There are various types of aquatic plants, each with its own needs. As such, there is no one size fits all answer on how much lighting they should get.

That said, it is generally recommended that aquatic plants should get around 8-10 hours of lighting daily. The light source could be indirect sunlight, fluorescent light, or LED light.

It is important to have a mix of lamps with red, blue, and green in their spectrum.

Also, keep in mind the number of plants in the aquarium and the ambient lighting conditions. For instance, a tank in an already well-lit room may not require additional lighting.


Intensity Of Light Required

For Easy Plants: 11-20 lumens (0.25 to 0.5 watts) per liter

For Medium Plants: 21-40 lumens (0.5 to 1 watts) per liter

For Advanced Plants: More than 40 lumens (1 watt) per liter



Too much light in your aquarium could spell doom for your plants. Make sure you grow plants that require the same amount of light together and turn off the lighting at appropriate intervals.

Do not place your tank in direct contact with sunlight.

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