5 Things You Need to Know About Planted Aquarium Lighting

If you’re getting into planted tanks, learning about lighting can be overwhelming. Keep reading to find out the 5 things I wish I’d known about lighting when starting my first planted tanks.

If you want to play with live aquarium plants, lighting is one of the key building blocks that you have to learn about. The goal with lighting is to grow plants, enhance their coloration, and of course minimize algae. When your lighting is out of whack with the available nutrients, your plants can end up failing to thrive or being covered with so much algae that you can’t see them anymore. So let’s dive into my top five list for lighting:

Tip #1 : Buy a planted tank LED light

Yes, you can use the default light that came with your aquarium kit or get a really cheap light, but I find they’re usually not strong enough or don’t last very long. Some people build their own LED lights, especially if they have a giant fish room with multiple aquariums, because lighting can get really expensive. But if you only have a few tanks like me, light companies like Fluval or Finnex are pretty good at what they do. Buying quality lighting from them ensures that your plants will get the full spectrum they require.

Homemade aquarium lighting by the King of DIY

Tip #2: Get a light that covers your entire tank

Some lights aren’t great at light dispersion or spread, which means the plants right underneath the light get lots of photons but the plants on the edges of the tank are pretty shaded. Now you can work around this by planting high light plants in the middle and low light plants on the edges. However, most people just get a better light or buy multiple lights if they have a large aquarium to cover.

Multiple lights used on large planted aquarium (source: American Aquarium Products)

Tip #3: Make sure your light is strong enough

Speaking of making sure all your plants get enough light, you also want to consider the brightness in your aquarium, especially if you have a deeper tank. You may hear people talk about a light’s PAR (Photosynthetically Active Radiation) rating, which refers to the light's strength. There’s a lot of debate on how much PAR is required, but the rule of thumb I’ve heard is that low light plants need 15-30 micromols of PAR, medium light plants need 35-50 micromols, and high light plants need over 50 micromols (plus CO₂ injection to avoid algae). Some products will list the PAR rating, but other times I’ve had to search online for the PAR readings that other hobbyists took. If you’re lucky, your local fish club may have a PAR meter that you can rent (because they’re super expensive).

Tip #4: Use an outlet timer with your light

Why do you need a timer? Because if you forget to turn on the lights enough, your plants will get sad and lose their leaves. If you give them too much light (or leave them on 24/7), you’ll have so much algae and green water, you probably won’t be able to see into your tank anymore. How long to turn on your lights really vary from tank to tank. If you have a ton of fast-growing plants in a high tech tank, you may leave that light on up to 12 hours a day. But if you have slow growing plants in a cold water tank in a room that already gets a bunch of ambient lighting, maybe you set your timer closer to 5 hours. Some people split up their lighting so that it’s on in the morning, turns off while they're at work or school, and then is on again at night.

Tip #5: Lessen your lights in the beginning

If you remember my previous post, I mentioned how new plants in your aquarium need time to acclimate to their new environment. During those beginning stages, they’re not going to grow a lot, so if you provide a lot of light, the plants aren’t going to use it as much, and algae is going to take advantage of it instead. Therefore, some people recommend starting your timer for only six hours a day for the first few weeks, and then gradually increasing to eight hours or beyond afterwards.

Bentley Pascoe said that if you have a dimmable light like the Fluval Plant Spectrum LED light, he actually dims the lights for his new plants. With an 18-24” tall tank, he starts off the light at 50% strength for the first two weeks, checks for plant versus algae growth, ups it to 65-75% strength if the plants are doing well, and then keeps increasing the light strength until he hits the maximum amount he wants. For shorter tanks, he’ll start the light off at 25-35% strength and then slowly increase from there. Genius!

Question of the Day

What’s your favorite type of aquarium light and how long do you have it on for? Comment below to share your experiences because I’d love to hear them. Take time to enjoy your aquariums and I’ll see you next time!

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