How to choose aquatic lighting: A test!

I have heard a LOT of different stories on aquatic lighting types and plant growth. From horror stories on blue light boosting algae growth to people buying the most expensive “Amazone”-type fluorescent lighting tubes for horrifying prizes. I did not want to join into all of these made-up or heard-of “facts”, and I decided to do my own testing! In this blog I will post what I did, and most important… the outcome of my test.

To have a healthy aquatic plant life in any paludarium or aquarium for that matter, lighting is important. So for my paludarium I set out to discover the world of aquariums and what is generally accepted for lighting there. Most people today are using fluorescent tubes for their sweet water aquariums. For me there were two drawbacks right there: Dimming them electronically is hard and/or expensive, and the tubes themselves cost a small fortune if you buy the ones most aquatic hobbyists do. I was amazed by the number of “Amazon” and “African” type fluorescent tubes. So African plants need different lighting from south America ones? Really??? Why not just use standard 830,840 and 865 colored lighting? Even further down the line: Why not use halogen or LED lighting?

Aquatic lighting: Everyone knows better

Everybody seemed to know better. Some really weird quotes and my responses:

Quote 1: “Never use lighting that contains blue light. It stimulates the growth of algae and is no good for an aquarium”
The discussion that lead from this statement was all about adding blue light to an aquarium. Using cold-white tubes were ok, but using a warm color (less blue) than adding blue using a dedicated blue source would cause algae to start growing. See where this is going? Exactly, nowhere 🙂

Quote 2: “Lighting for plant growth NEEDS to be matched to the spectrum where chloroplasts are sensitive for”
Another nice one. There are complete studies on the spectrum where chloroplasts are sensitive for. Then light sources are created to closely match this, hoping plants will grow at their maximum. But who is saying that is what plants need? Why couldn’t they do better for example when they receive infrared as well? No one could actually answer that one.

“LED lighting will never work for an aquarium because it is just not bright enough”
Another cool one. I got my hands on some LEDs at the time (and this test was originally performed in december 2005!) that would consume 1Watt of energy, but where too bright to actually look directly into. Stacking up these LEDs surely should give me enough light I figured. But at the time (and even today) very little people are actually testing LED lighting for aquariums.

A bold statement on aquatic lighting

Following all of the discussion like the ones above, I figured plants are probably not all that complicated to light properly. After all, the sun has always been their role-model, and I figured they have optimized to this type of lighting. So here goes the bold statement:

“It does NOT matter what spectrum of light you throw at a plant. Just make sure you throw enough light, and the plant will figure out what he needs”

After having thought up this bold statement, I figured to make my life easy. I did not want to go and figure out what light frequency would do what, but I decided to go the hands-on way: Select useable lighting, and get your hands dirty in testing it!

And that is exactly what I did. Up first, the selection of lighting to test.

Light type 1: PL lighting

PL lighting is considered to be useable for aquatic plant growth. Its spectrum is much like ordinary fluorescent tubes. So I had every reason to add this type of lighting to my test. Maybe just as a “control group”. This is the PL I used:

Light type 2: Halogen

The first lighting I wanted to test apart from a control group is halogen lighting. It is by far my favorite type of lighting.

Shown here is the halogen combined with a blue LED spot. It is like a ray of sunlight. Very beautiful. But how do aquatic plants react to it? Little is known. I got some quote from someone who stated “Halogen lighting has dips in the spectrum exactly where chloroplasts are sensitive for. Therefore halogen lighting is particularly bad for plant growth”. I feel a test coming up!! So I decided this would be light source number two to test (20W).

Light type 3: White LEDs

I wanted very much to test the lighting with LEDs. They last ages (20.000 hours plus), they are very energy efficient. At the time you could (almost only) buy LED spots containing 16-20 regular white LEDs.

I decided to use three of these together as lighting source three for my tests. I choose to use three of them because they use (and deliver) far less energy than the other light sources.

Light type 4: 1W Luxeon LED

Very new technology at the time (and hard to get in 2005) were the Luxeon LEDs. Nowadays you have more vendors delivering this same technology (like Cree, SuperLED and Zleds).

The amount of light coming from this single LED was immense. So immense, that I decided to use just one single 1W Luxeon LED for light type four for my test.

Setting up the test

The idea was relatively simple: Get four small tanks (40x20x20 cm), fill them up with the same sand, add three Corydoras to each tank (Corydoras Aeneus was chosen because they are cheap, hardy and they can eventually live in the paludarium) and finally plant a single true aquatic plant in the center of the tank (I choose to use Echinodorus Magdalenensis; not the easiest one to grow but one of my favorites)

Then I would just add one type of lighting to each tank. Finally, take a picture with fixed settings on a daily basis. Do this for 30 days, then compile a video of the shots I took. Sounds simple enough.

This are the general setup steps I did:

  • Fill each tank with 3cm of crusher sand;
  • Fill each tank with tapwater;
  • Use AquaSafe to remove any nasty ingredients from the tapwater;
  • Plant the Echinodorus plants;
  • Get lighting in place and time it for 12 hours of lighting every day;
  • Keep the water temperature at 24 degrees;
  • Wait half a week, then introduce the fish;
  • Take four photos with a fixed white balance on the camera (!) every day around the same time of day.

Easy right?

The outcome!

For the human eye the halogen lighting delivered most light. The three “regular” white LED spots deliver the least light. But will the plants “see” this the same way?? Time would tell!

After twenty days of photographing each tank, some very different things in each tank were noticeable. In a table:

Tank number Used lighting Observed plant growth Observed algae growth
1 PL-Light 15W +++ +++
2 Halogen 20W +++ ++++
3 Reg. CW* LEDs 18×3 ++ ++
4 Luxeon CW* LED 1W ++++ +

* CW = Cold White, color temperature around 5000-6000K)

Amazing to see! The PL-lighting did ok. Halogen did just as well, but with a lot more growth of algae. Very comparable to algae growth when your aquarium catches the morning sun every day.

The regular LED spots did not do well. Even though I used three spots, there still wasn’t enough light produced. This is why there is hardly any plant or algae growth.

The Luxeon LED did remarkable: The plant growth was really really good, but algae where nowhere to be found! This type of lighting actually has the most blue light in it, and this proves that algae are not necessarily triggered by this. Also noticeable was, that the plant in tank 4 build a lot of beautiful somewhat smaller leaves, and all leaves build a beautiful crown without any signs of stretching for the light.


Bonus: View the animations for all four tanks!

Finally, you can watch the animations of each plant as they grow from day 1 to day 20. I marked the first day in the animation so you know when to start looking:

Test 1: PL 15W lighted plant test (20 days)

Test 2: Halogen 20W lighted plant test (20 days)

Test 3:Traditional cold-white LED spot lighted plant test (20 days)

Test 4: Luxeon 1W Cold-white lighted plant test (20 days)

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