Why Does Aquarium Sand Turns Brown? (7 Ways To Prevent It)

Image of overgrown brown algae

Aquarium sand turning brown is a common problem in new aquariums. However, it may also occasionally show up in older tanks. So, why does aquarium sand turns brown?

Aquarium sand turns brown because of the excessive growth of brown algae or diatoms in the aquarium water. These microorganisms appear in newly set up aquariums as well as in aquariums with insufficient lighting. Brown algae can also occur in aquariums containing high levels of silica and nitrate.

Let’s take a deeper look at this now.

What Are Brown Algae?

Different types of algae grow in aquariums. Of these, brown algae or silica algae are responsible for turning aquarium sand brown.

Now, the term “brown algae” refers to a type of unicellular organism called diatoms.

Technically, they are not algae. These organisms appear in both saltwater and freshwater habitats.

Diatoms may be present in your aquarium, but you may not notice them.

They become noticeable when they reproduce profusely and create a “diatom bloom.”

Diatoms need silica to survive and are attracted to sandy substrates.

Silica is a naturally occurring compound of silicon and oxygen, and it is abundantly present in the sand.

Diatoms use silica to build tough outer walls.

Now, brown algae don’t create many problems like other common varieties of algae.

They don’t harm fish and other aquatic creatures. Nonetheless, their presence is not good in an aquarium.

Should You Worry About Brown Aquarium Sand?

Any change in the color of the water or sand of your tank deserves attention.

So, don’t ignore it when your aquarium sand turns brown. It most likely indicates the presence of brown algae or diatoms.

The main problem with diatoms is that they make the tank look dirty. They may also spread across the tank.

Nonetheless, brown algae are not particularly harmful. They usually go away on their own.

However, your tank will continue to look unappealing if you decide to wait it out.

Additionally, these organisms feed on resources like oxygen and nutrients in the tank, reducing their availability for your aquatic pets and plants.

So you may want to speed up the process of eliminating them.

Recommended Further Reading:

What Causes Brown Algae Blooms?

Most tank owners notice the presence of brown algae in their tank only when there is a bloom, and it covers most of the surfaces.

Brown algae blooms usually occur under the following conditions.

1. The tank is new.

Brown algae or diatom blooms commonly occur in newly cycled tanks.

When a tank completes its biological cycling, its nutrient balance gets thrown off.

Diatoms tend to appear when the nutrient level of the water increases.

These tiny organisms feed on available nutrients and multiply profusely.

They attach to the substrate, rocks, tank decorations, and other tank surfaces.

Although these diatoms will clear on their own, it can take anywhere between a few days to a few weeks.

2. Improper lighting.

Brown algae commonly appear in tanks with excessive or inadequate lighting.

Diatoms can survive in conditions that are not optimal for regular aquatic plants.

They adjust to both excessive and inadequate light conditions.

So you may notice them in brightly-lit tanks.

However, in bright tanks, they may have to compete with other algae like green algae.

Aquatic plants will be unable to perform photosynthesis if a tank doesn’t have enough lighting. So they may perish.

However, diatoms can easily meet their survival needs in such conditions. Hence, they thrive in dimly lit tanks also.

3. Water chemistry problems.

Diatoms occur in new tanks where the nitrogen cycle is not yet stabilized.

However, you may also notice them bloom in established tanks when the water chemistry levels are off.

When the silica and nitrate levels of a tank increase, it favors brown algae growth.

Medications and other added substances may also alter the water chemistry of the tank.

If you add any medication or salt to the tank to treat infections or other conditions of your aquatic pets, they can alter the mineral content of your tank water.

They will introduce nitrates and silica into the water, and diatom blooms will follow.

The brown dust that begins as patches in your substrate will slowly spread and take over more areas of the tank.

So check the label of any additives you put in your tank. Diatom blooms may occur if any of these substances introduce silicates into the tank.

4. New substrate addition.

Diatoms bloom in tanks with high silicate levels. The silicate level of the substrate will increase if you add fresh sandy substrate.

In most cases, you will see diatoms until they feed off the silicates in the new substrate. This may take several months.

Related Further Reading:

How To Prevent Aquarium Sand From Turning Brown?

Aquarium sand turns brown due to brown algae. You can prevent it by identifying the cause and addressing it promptly.

The following techniques will help you prevent the aquarium sand from turning brown.

1. Frequent water changes.

Frequent water changes are necessary for good tank hygiene.

By changing part of the water in a tank, you can also get rid of nitrates, phosphates, and organic waste that is dissolved in it.

This reduces the number of nutrients that the brown algae need. When the diatoms starve, they will perish.

2. Clean the substrate.

Brown algae typically adhere to aquarium sand and other tank decorations.

You can eliminate them by cleaning the surface of the sand.

Either use an aquarium gravel vacuum cleaner or clean the substrate manually to eliminate the diatoms.

3. Scrub the glass and surfaces.

You can scrub the glass and tank surfaces to remove any diatoms attached to the glass or substrate.

Brown algae have a gritty texture and are hence easier to remove than slimy algae.

You can scrub them off using a sponge or scrubber and wipe the surface clean.

4. Introduce algae eaters into the tank.

Several freshwater and marine algae eaters can fix your algae problem.

Add these animals to your tank, and they will feed off the brown algae.

In a freshwater aquarium, nerite snails, amano shrimp, and some varieties of catfish and plecos can control brown algae growth.

Trocus snails and Mexican turbo snails are good choices for marine tanks with brown algae.

5. Improve filtration capacity.

Algae growth happens in tanks with insufficient filtration.

When you add new fish or aquatic plants, the bio-load of the tank increases.

So you may have to upgrade your filter to cope with the increased load.

If the filter can’t keep the tank clean, uneaten food and leftover organic waste can release nutrients into the water.

These will help the algae flourish.

Improving the filter capacity or cleaning it frequently will fix the problem and prevent diatoms from growing.

6. Increase the water flow.

Brown algae are not fond of fast currents. They prefer slow-moving water.

Increase the water flow in your aquarium by changing the filter setting or using a water pump.

This will discourage the brown algae from anchoring to surfaces and reduce their chances of survival.

7. Use a UV sterilizer or RO filter to eliminate the diatoms.

UV sterilizers are specialized aquarium equipment to get rid of parasites, algae, and other microorganisms in an aquarium.

They will neutralize any diatoms in the water and keep your tank clean.

Similarly, you can use a RO filter to keep the silicate, nitrate, and phosphate levels of your tank water under control.

You can also use suitable chemical media to neutralize phosphates, nitrates, and other nutrients to free the tank water of diatoms.

Interesting Further Reading:

Why Does The Sand In Saltwater Tanks Turn brown?

Diatom blooms also happen in saltwater tanks.

They not only make the tank look ugly with their gritty presence but also deplete the oxygen in the water.

Some marine aquarium hobbyists don’t mind their presence. However, it’s not wise to overlook diatom blooms.

If you leave it unchecked, these organisms can cover corals and live rocks and suffocate them.

In addition, diatom blooms can destroy the visual appeal of a tank and make it look dirty.

Fortunately, the same techniques to eliminate diatoms in freshwater tanks will also work in marine tanks.

You can control diatom blooms by improving the water quality, increasing filtration, and performing water changes.

You can also increase the lighting or use a UV sterilizer.

Bottom-dwelling algae eaters will also help fix the issue by eating diatoms in the substrate and preventing it from spreading.

Another way to eliminate brown algae from a marine environment is to use a protein skimmer.

Protein skimmers use tiny water bubbles to produce foam in the water.

This foam adheres to waste particles in the water, like organic waste produced by fish and uneaten food.

The foam then rises to the top of the skimmer, where it gets collected along with the contaminants it carries.

This is how protein skimmers get rid of the organic waste before it breaks down and releases toxins and salts into the water.

By doing so, they also cut access to nitrates, phosphates, and silica that diatoms need to thrive.

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