Color blending is how all the individual light spectrums from different bulbs and individual LED diodes blend together to create a uniform light spectrum and appearance in your aquarium. If you have ever seen spots of color dance across the white sandbed in an aquarium, you have seen what poor color blending looks like.

Why Does Color Blending Matter?

There really are two reasons that effective color blending becomes a topic of concern for aquarists.  Does it play a role in the biological health of the coral and does it look good in our tanks? 

Red Sea 750 XXL at Bulk Reef Supply

Color blending and its role in the biology of a coral is something that for all intents and purposes is incredibly important because, after all, healthy coral is what we are all striving to achieve. Truth is, we don't have a great answer that is backed by peer-reviewed science to specifically support the idea that color blending is important to a coral's health. Without effective color blending, the corals are hit with constantly shifting spectrum peaks throughout the day and there really isn't any research being done to investigate how this may or may not be affecting the coral.  

While this doesn't leave us much to work with in the way of making educated decisions in our tanks, there is a more tangible reason we are concerned with color blending which is the appearance. Poor color blending in an aquarium creates a less-than-desirable viewing experience that can be quite distracting. The result is dancing beams of color that flutter and shift as the light is reflected across the moving surface of the water. We have dubbed this poor color blending the "disco effect" because of its likeness to a 70s-era disco club. 

Lighting showdown experiment


The Experiment

Each of the 50 different lighting options was mounted over the top of a 24" cube-shaped aquarium at the ideal mounting height. We added a powerhead to create surface water movement and most closely resemble a reef tank. Using a spectrometer, we took 20 consecutive snapshots of the color spectrum to capture any shift that may occur over time.  

A well-blended spectrum will not display any noticeable shift in color spectrum peaks between the various shots while a poorly blended spectrum will show constant shifts in the various spectrum peaks. As was evident in the test, there are varying degrees of severity which can be visually witnessed by the varying degrees of light artifacts that show up in the aquarium. 

Which Lights Blend Color Most Effectively?

Here are the results based on the various types of lighting we tested. Pay careful attention to the different types of diffusion and approach to color blending to learn more about which may suit your desires best. 

1. T5 fluorescent lighting displayed the best results with no noticeable shift in color spectrum between all 20 of the spectrum snapshots. Even with different colored T5 lamps used side by side, the blended phosphors, large light sources, and wide reflectors create a very uniform and even distributed spectrum throughout the entire aquarium. While you shouldn't expect any kind of shimmering effect or reflection lines, the coverage, shadow reduction, and easy implementation of T5 Fluorescent lights on a reef tank are hard to beat. 

Neptune Systems Sky LED

2. Large module LEDs with diffusion panes or lenses produced the best results among the LEDs. The Neptune Systems Sky and Radion with diffuser panes covering the diodes produce this well-blended spectrum and remain to be among the best-performing LEDs across our entire lighting showdown series.

Recessed Diffusion Lenses

When using diffusion panes that cover the LED diodes with a frosted acrylic or similar lens material, there is a trade-off in performance that comes at the cost of PAR. There is also a relatively new approach to diffusion which is a clear acrylic lens with each individual LED diode housed in a recessed pocket. The recessed pockets act as a color-mixing chamber and the acrylic itself emits diffused light. The Aqua Illumination Blade LEDs take this approach which results in a decent blending effect and a soft natural shimmer without a significant reduction in PAR as we see with "frosted" diffusion lenses.

Kessil A360 LED

3. Dense Matrix LEDs under a single lens like the Kessil do a decent job of blending spectrum because all of the light is mixed together under a single lens. This approach produces a brilliant shimmer as well but struggles with shadowing because of the single source of light emitted at a single angle.  

4. Individual lenses covering each LED diode result in single beams of light that don't blend together well and produce the largest degree of variance between the spectrum snapshots.

Caveats to consider...

The spectrum test we performed can be "cheated" or misleading if the blue spectrum peak is very narrow. If an LED only contains royal blue and cool white LEDs, the blue peak will be narrow and won't display a noticeable change in the spectrum blending.  That being said, this narrow blue peak is not the ideal spectrum we desire over our tanks making it a less-than-ideal solution regardless. 

Using fill light alongside a primary LED can help improve color blending as seen in the Prime and Prime + Blade results.  The addition of the Blade strips alongside the Prime resulted in better color blending performance and helps to fill in disparities between color peaks.  

6 Types of Shimmer

The disco effect and shimmer are essentially the same things, both are lighting "artifacts" created in our tanks by the light but they differ in appearance. What we classify as a desirable shimmer and ugly disco effect is somewhat subjective. Throughout our tests, we were able to ID 6 specific types of shimmer based on the lenses used to diffuse or blend the light. You can use this as a guideline for choosing an LED and deciding which look you prefer inside your own tank.

  1. Focused individual lenses create tight beams of light and the most drastic "disco effect" with dancing rays of color throughout the tank - Orphek
  2. Large arrays of low-power LEDs create what appears like a "static tv" effect on the sand bed. Less of a shimmer and more of a fuzzy appearance. - AquaMaxx Prism
  3. Large arrays of high-powered diffused LEDs and T5 Fluorescent fixtures create almost no visible shimmer - Neptune Sky and Radion with Diffusion Pane
  4. Single-point source LEDs under a single lens create the most distinct brilliant shimmer that can be adjusted by changing the surface movement - Kessil
  5. Using single-point source LEDs (Kessil) with soft fill light (T5s or LED strip lights) together creates a balanced shimmer - T5/LED Hybrid fixtures
  6. LEDs using the recessed acrylic lens without a diffusion pane produce a balanced shimmer similar to LED/T5 hybrid - AquaIllumantion Blade