Does Substrate Color Affect Fish Color, Health, and Behavior?

Aquarium substrate is massively influential as is! It is essential for the looks of your aquarium. Everything rests on its colors, shapes, and properties.

But it has more aesthetic implications than first catches the eye.

Does substrate affect fish color?

Does it change plant color?

Well, it certainly isn’t only a matter of perception.

Aquatic plants don’t actively change colors. Their colors do change, but it is an involuntary action. The plants’ shade changes due to diet and light.

Fish, on the other fin, can and do change colors based on the environment in much more interesting ways. They react actively to the environment, trying to blend in through various tactics. Changes in pigmentation is one of them and the bottom of the tank plays a huge role in that.

Depending on substrate color, some fish can change their colors. When it happens, the change often is aligned with the color of the substrate. Certain species might shift toward paler nuances in bright sand or white pebbles. Conversely, dark substrates make colors more saturated and pronounced.

In species like black plecos, the difference is dramatic, while in others there is none. All the same, knowing what color substrate your fish prefers will help them display their true colors and, potentially, live a happier life.

Let’s break down how exactly substrate color affects fish and plants.

Fish Color and Appearance

Substrate is the single largest coloration in your tank. It usually covers the entire bottom and, especially in new tanks, large portions of it remain exposed.

Some fishkeepers use backgrounds, either pretty pictures, paint, or water-resistant wallpapers. They can become more pronounced color elements. Especially for human eyes and behavior.

See, peaceful fish usually are hunted from the top or the bottom. In nature, obviously. I hope none of you, dear readers, use fish tanks to feed your pet falcons.

But in the wild, most fish swim across dirty, dark, muddy bottoms. Their dark backs make them hard to spot when looking from above.

Mimicking such a natural feature with dark gravel or enriched substrate is likely to make the fish show their true colors. Dark substrate stimulates genetically innate beauty. It doesn’t happen in all species but plecos react to different backgrounds very obviously and rapidly, as you can see here:

When you put certain species in bright aquariums, their color also pales rapidly. As with the plecos above, it seems to be largely driven by fish built-in adaptation.

Fish scales often contain cells that refract light in unimaginable ways. Putting a fish on a bright and then black background won’t simply change the perception of the fish the same way moving a sheet of paper from a light to dark background would alter our perception of its colors.

Quite literally, the fish will look different due to the intricate complexity of its scale-cells. What’s more, fish see differently than us and many species perceive parts of the light spectrum invisible to the human eye. The ability to reflect light in a way that turns you invisible is a powerful surviving mechanism that ties in directly to the fish’s overall environment.

Do Fish Get Stressed on Inappropriate Substrates?

Certain fish species get considerably brighter when living on bright substrates. How much is light refraction and how much is it because the fish feels stressed by the bright setting that exposes it to imaginary predators from above?

It is a complex topic that still relies on suggestions rather than certainties. All the same, the supposition that fish will look better and live longer in a habitat built for them is hard to argue against.

It is hard to tell whether an “unnaturally” colored substrate will stress fish. What if they had grown on bright surfaces? Just like their parents before them, and theirs before that.

All the same, the margin for error with more natural (for the fish) setups is bigger.

Does Substrate Color Affect Fish Health?

It is hard to tell with absolute certainty whether substrate color affects fish health, but most likely it does. The scientific literature is somewhat inconclusive, but all data points toward the fact that conditions that mimic the fish’s natural habitat help.

In the majority of cases, this means darker substrate color. How many lakes or rivers have you seen sporting brightly colored bottoms, full of fish? Even the high-altitude lakes in the Andes, which have rather clear and transparent water, have dark beds. Bodies of water in the tropical areas of South America and Asia, where the majority of tropical fish in the hobby come from, are dark and murky.

I will always caveat the assumption that what is normal for the wild fish is best for their aquarium counterparts because the latter often are bred for generations in captivity. Their natural habitat has become a glass box, sometimes without substrate.

All the same, a few hundred million years of evolution have coded certain predispositions in the fish toward ideal living conditions. Trying to provide them doesn’t hurt and will likely help the fish live longer and happier lives.

Besides impacting the fish color, darker substrates often provide an added sense of security. It helps fish feel safer, with more places to hide and rest.

But fish’s health is not the only one impacted by substrate brightness.

Substrate Color Affects Water Plants

Substrate mixtures are essential for the health of your water plants. There are inert substrates like sand or gravel that are good for plants, and there are enriched soils that are designed specifically to promote underwater shrubberies.

But that’s not all.

Bright substrates reflect much more light than darker ones. To make matters even more complicated, there are dark gravel and pebble substrates that are glossy. Their stones are, say, black, but with shiny surfaces that reflect plenty of light.

Shiny, colorful stones
Photo by Jatin Saini on Unsplash.

This reflected light hits the plants on the underside of their leaves. Now, this could be a good thing, as it essentially increases the potency of the lamp you have in place. On the other hand, it could cause algae problems, as the reflection becomes a light source that is hard to account for.

Few fish appreciate reflective substrates. They can be disorienting and reduce the fish’s natural camouflage. The main reason why almost all fish have white bellies is the protection it provides from predators lurking at the bottom.

Spotting clearly the white tummy against the bright backdrop of the surface is not an easy task. Reflected light does make fish more visible from the bottom, which is not ideal for the little swimmers.

Substrate Color Affects Fish and Plants

The color of your substrate affects both livestock and plants. Fish tend to prefer darker substrates, even though species like the lemon tetra are more comfortable in brighter setups.

Before buying new fish, check a few photos online to gauge on what type of surface the pictures are taken. This will give you a very good idea of whether your substrate is of a similar hue. If it is radically different, the fish might not display the colors you are buying it for.

As for plants, take into account the amount of light the bottom of your tank reflects upon the leaves. If it’s too much, algae will soon start spawning, possibly at the bottom of the leaves, suffocating them insidiously and stealthily.

All in all, substrate matters a lot for any tank setup. It impacts how plants will grow, how the tank will look, and how the fish inside will look and feel. The good news is that there are plenty of substrates to choose from. Let your imagination fly, tie it to a good amount of research, and get the fish that tickle your fancy.

Provide your fish with a setting that is closer to their natural habitat and they will be happy and secure.

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