Do Aquarium Plants Need Sunlight?

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All aquarium plants, and plants in general, need sunlight to perform proper photosynthesis.

The photosynthesis process is specific to plants, algae, and some forms of bacteria and consists of turning sunlight and CO2 into carbs and oxygen.

The process is vital for plants since their entire physiology functions are based on photosynthesis.

The plants’ green color is a great indicator in this sense since the chlorophyll responsible for it is designed to attract more sunlight during the day.

Now that we’ve established that sunlight is key to plant health, we should now discuss the specifics.

These include the light intensity, light duration, day/night cycle, and other factors that will differ depending on your tank setup and plant species.

How Many Hours of Sunlight do Aquarium Plants Need?

All aquarium plants require a stable day/night cycle and between 10 to 12 hours of sunlight daily. This is enough to support the plant’s physiological activity, which is crucial not only for the plant itself but for the environment as well.

Healthy aquarium plants will provide your aquarium life with a variety of benefits, such as:

  • Inhibit algae growth – Algae typically bloom in environments with a lot of phosphates and dead organic matter. Interestingly enough, plants also use these components as nutrients, effectively starving the algae population and inhibiting their growth. This is generally good because, while algae won’t alter the water’s chemistry or hurt the fish or plants directly, they will have a problematic impact long-term. Overgrown algae will spread throughout the environment, cover the plants, restrict their access to sunlight, and create nutrient competition.
  • Oxygenate the environmentLive plants are a crucial balancing factor in any aquatic system. They will consume CO2 and produce oxygen during the day and reverse the process when lights go off during nighttime. This will maintain a stable chemical balance, allowing fish to breathe better and remain healthier long-term.
  • Provide protection – Live plants provide protection and secure and comfortable spawning grounds for your fish. They will also serve as hiding areas for the fry until they are large and strong enough to join the general population. Fish living in planted aquariums tend to be more sociable and daring and exhibit brighter colors than those in barebones setups.

To get these benefits, you need to make sure that your plants are getting sufficient light time during a 24-hour period.

Can Aquarium Plants Survive Without Sunlight?

Some aquarium plants will survive without sunlight just fine. It’s just that they require some light source to compensate for having no sunlight access.

So, in essence, we have 2 primary aspects to consider:

  • No sunlight – No sunlight doesn’t mean no light at all. It just means that your plants don’t have direct access to sunlight, which is fine considering other light sources are available. Plenty of aquarium plants will thrive despite not having access to natural sunlight. These include species like Amazon sword, Brazilian waterweed, valisneria, etc. The trick is to provide your plants with a stable light source so that they can perform their photosynthesis.
  • No light source at all – This is the extreme version of ‘no sunlight.’ In essence, we’re talking about your plants having no access to any form of light, which is obviously a no-no. Plants cannot survive more than several days without light. Hardier species will probably last up to a week without light, while more sensitive plants won’t last more than 2-3 days. So, ensure all your aquarium plants have a steady light source and a stable long-term day/night cycle.

To summarize, no, aquarium plants won’t survive without light, but will survive without sunlight, provided they’re still getting the lighting necessary to perform their basic functions.

Is LED Light Enough for Aquarium Plants?

Yes, LED lighting is sufficient for aquarium plants, provided you stick to the recommended wavelengths and intensity.

An interesting point here is that there’s a difference between the type of light fish need compared to what plants require. When it comes to fish, any type of LED lighting is sufficient.

The goal is to provide your fish with a steady day/night cycle and light up their environment so you can see them better. It’s as basic as it gets. When it comes to plants, the light’s wavelength also comes into play.

Technically, most aquarium plants will do just fine with regular LED white light. However, the optimal setup should consider a specific wavelength equation.

The perfect mix of LED wavelengths for aquarium plants includes 50% red light between 630 and 700 nanometers, 35% green light between 500 and 580 nanometers, and 15% blue light between 435 and 495 nanometers. Naturally, these values are more difficult to achieve, but they may be worth it long-term.

If it sounds like too much commitment, you can stick to the regular white LED since that’s typically enough to support your plants’ physiology.

A more important point, I think, is managing light intensity, and we’ll discuss this one next.

Signs of Too Much Sunlight on Aquarium Plants

It’s worth noting that not all plants require the same amount of lighting. Fast-growing plants demand more light than slow growers since the former are in need of more nutrients overall.

But, even in their case, there can be such a thing as too much light.

So, consider the following:

  • Too much light, too few nutrients – The more light you add to your tank, the faster and larger your plants will grow. But there’s a problem. Because of this accelerated growth rate, your plants will also require more nutrients. Providing them with too much light but not enough CO2 or other nutrients can actually cause plants to die off. It’s counterintuitive, but nature is like that sometimes.
  • Excess light hurts slow-growing plants – Slow-growing plants don’t need as much light as other plant species. Providing them with excess light will open the door to algae and inhibit your plants’ growth even further. Always choose your plant carefully, based on your aquarium setup and available environmental conditions.
  • Overall risks – Having too much light in your tank will always come with the risk of algae bloom. It doesn’t matter what types of plants you’re housing. Always be mindful of this downside.

But what are the tell-telling signs of too much light in your aquarium? The best one to consider is the algae bloom. More specifically, we’re talking about algae covering your plants primarily.

This is a sign that the light intensity is too high, allowing algae to grow faster and absorb more nutrients from their environment.

Always check the light source first if you notice algae overgrowth in your aquarium.

Tweaking the light may be the most effective algae control mechanism at your disposal at that point.

Do Floating Aquarium Plants Need Sunlight?

Yes, floating aquarium plants need sunlight too. They are no different than the rest of the plants in this sense. However, there is an issue worth discussing at this point.

Floating plants can grow quite large, provided the optimal environmental conditions. We mention surface plants like duckweed here too.

The problem is that overgrown floating plants will actually end up hurting the environment, especially if you also have rooted plants in the same habitat.

The larger the floating plants get, the more they will restrict sunlight from reaching the tank’s lower regions.

This can prevent rooted plants from getting the light they need. To prevent that, make sure you trim your floating plants regularly.

Conclusion

All plants demand sunlight daily to perform their normal physiological processes. The only difference is that some aquarium plants require more lighting than others.

So, make sure you understand each plant’s lighting and nutrient demands before committing to anything.

We’ve already discussed the risks of excessive aquarium light, while those of light deprivation are rather obvious – slow and agonizing death.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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