Over a decade of fishkeeping experience, I have dealt with more than a dozen types of algae. The fuzzy black mold that grows in my fish tanks and is stubborn, is the one I fear most.

If this unwanted guest has found a home in your fish tank, you’ve come to the right place. This blog will explain everything, from the causes of black mold in fish tanks to how to remove it and prevent it from happening again.

Let’s begin!

What Exactly Is Black Mold That Plagues Our Aquariums?

The dreaded black beard algae is the most common form of black mold found in tanks. This fuzzy black mold is actually a member of the red algae family that grows in high-phosphate environments. It can be removed temporarily, but it will come back if you don’t find a permanent solution.

In the beginning stages of development, black molds can be seen. It grows a beard when it matures and attaches itself to rocks, decorations, and plants.

What Is The Black Mold’s Texture Like?

The black mold was so soft that I touched it. Despite its rugged appearance, the algae is extremely soft to the touch and slippery. It feels almost like you are handling dark, wet hair.

What Causes Black Mold In Fish Tanks?

Black molds in fish tanks are caused by high phosphate levels in the water. Phosphorus is essential for algae growth. Wear-out fluorescent lamps, which encourage algae growth rather than requiring plants, could also be a possible reason. Black molds can also be caused by untreated tanks that have high levels of toxic buildup and pollution.

What Aquariums Are Prone To Developing Black Molds?

Old Victorian plumbing is more likely to lead to black mold growth. To prevent the corrosion of potentially dangerous lead pipes, water authorities have added a high level of phosphate to the water.

Black molds can develop in aquariums that aren’t properly maintained. Even if we keep our tanks clean, they can still appear.

Are Black Molds Harmful For Fish?

Black molds can be unsightly, but they are not dangerous for fish. They don’t release any toxic chemicals into the water. Some fish will even hide or play with the algae, and sometimes nibble on it.

Algae overgrowth can cause oxygen to be depleted and block sunlight. The fish’s health will be affected by the imbalance in their nutrient levels.

It is best to get rid of black mold as soon as it appears.

Are Black Molds Harmful For Plants?

The leaves and stems from slow-growing plants such as anubias and java fern are often where black molds first appear. Although the molds won’t release any toxins into the water, they can outcompete your plants, causing them to lose their nutrients and eventually, even causing them death.

It is imperative that you get rid of molds as soon and as possible.

This brings us to the next section. Continue reading!

How To Remove Black Mold In Fish Tank?

It is difficult to remove black mold from fish tanks because it loves to return. To eliminate it, you must get to the root of the problem. Your best option is to reduce the phosphate content in your tank. It is also possible to get rid of solid waste and perform frequent water changes. Last but not least, change your old bulb.

Step-By-Step Guide To Remove Black Mold From Fish Tank

This guide is a compilation of my personal experience with other hobbyists. It provides a practical solution. It’s pretty certain to work. You will need to dip the decors in hydrogen peroxide. This will remove phosphate and inhibit the mold’s ability to photosynthesise.

Step 1: Wash Your Hands And The Tools You Will Use

Wash your hands well. If you plan to use the buckets, hoses or other tools, don’t forget about washing your hands.

It is not a good idea to accidentally expose fish to contaminants that could potentially endanger their lives.

Step 2: Remove The Fish And Invertebrates

Transfer the fish to another tank. It is important to make sure that the water parameters of their temporary home are identical to the main tank’s.

Fish can be shocked and stressed by sudden or large changes in their environment. This can make cleaning impossible.

Step 3: Clean The Tank Lid

Place the lid a bit further away from the tank and tank contents. The lid should be sprayed with undiluted vinegar. Next, wipe it clean. An old toothbrush, sponge or paper towel can be used. I prefer to use a toothbrush.

Rinse the lid and apply more vinegar. Let it rest for approximately 2 minutes. Next, rinse the lid and wash it with hot water. Rinse the lid until vinegar has completely dried.

Allow the lid to dry while you do other tasks.

Step 4: Sort Out The Decor

All decorations, including gravel and pebbles, must be removed and placed in a large container. You can also use hydrogen peroxide (3%), to submerge everything.

Anubias and Java moss, which are sensitive plants, may be most affected by the harsh chemical properties of the compound. You can place them in separate containers and mix hydrogen peroxide with water at a ratio of 1 to 3.

Bleach can also be used to treat plastic plants in a ratio of 1/20.

Let everything soak for about 3-4 minutes, then rinse with warm water.

Peroxide leaves virtually no residue. You can immediately return everything to the tank if necessary.

If you don’t want to use chemicals (I get it), you can immerse everything in boiling water in a heat safe container.

Then, you will need to scrub the area with a toothbrush. Rinse with hot water. Repeat the process of rinsing and scrubbing as necessary.

Step 5 – Clean the Tank

An aquarium siphon will be used to drain the water. If the infestation isn’t too severe, you can leave 50% of the water in the tank. Siphon it and toss it.

To remove any algae or mold from the tank’s inner glass, use the algae scraper. To scrub the glass surface, you can also use an old toothbrush and some water. Don’t forget hot water to rinse the tank’s sides and then siphon the liquid out.

Next, clean the filter by changing the cartridge. All decors should be returned to the tank.

As needed, fill the tank with water. If necessary, add dechlorinating and phosphate removal agents. To avoid poisoning fish, make sure you follow the manufacturer’s instructions.

It will take at most 24 hours for the temperature and other parameters to stabilize safely.

After the water has been boiled, the waiting period is over, you can gently return the fish to their tanks.

What is phosphate?

I won’t get into the jargon. However, phosphates (PO4) can be considered a byproduct of almost everything that is left behind in a tank. This could be leftover food, feces, or decayed plants and alga.

Although fish can be affected by phosphate buildup, corals and invertebrates are the most vulnerable. You already know that phosphate, which is also the main food source of many types of algae, includes black mold, is a major factor in their survival.

The best thing about phosphate? It’s almost always present in aquariums around the globe. We may not even be aware. At lower levels, it’s harmless. However, phosphate levels continue to rise and can have a devastating effect on fish and plants.

As wastes are eliminated, the naturally increasing levels of phosphate in the tank will cause them to increase. Both internal and external sources of phosphate are available.

Causes Behind Phosphate Spike In Tank

Let me give you a list of them:

• Dying alga
• Leftover food
• Decaying Plants
• Fish feces
• Carbon filter media
• Tap water
• kH buffers
• pH buffers
• Aquarium salt
• Imbalanced Nutrition
• Wrong lighting

Isn’t the list obvious enough? For the sake of this blog’s length, I won’t go into detail about each one. There are some points that caught my attention.

High Phosphorus (PO4) Content In Tap Water

Authorities must use high levels of phosphate to prevent lead corrosion in areas where there is still much reliance on older lead plumbing. This can have dire consequences if not taken care of. If you notice black mold growing in your tank, you need to test the phosphate levels.

Tap water may be the cause of phosphate or black mold growth in your tank. You have two options.

Water that has been reverse osmosis purified or distilled will be required. This will ensure that the black molds are not able to grow. This will remove all minerals, both good and bad. To treat the water, you’ll need to use a mineralizer before adding it to your tank.

While researching for this piece, I came across this phosphate free mineralizer from Seachem and instantly added it to my cart.

A phosphate-absorbing medium can be used to filter your water. This type of media should be used at least five times an hour.

I would choose a powerful canister filter for this.

Imbalance of Nutrients

Black mold can be caused by a tank’s imbalance in nutrients. This is a less well-known but still very common reason. A lack of carbon dioxide, for example, can lead to the growth of black beard algae.

Your aquatic plants will not compete with the algae for food because of their inefficient and weak photosynthesis.

Wrong Lighting

Only a few aquatic plants require lighting for more than 8 hours. Make sure you don’t leave the lights on longer than this.

Algae can appear when there is an imbalance between the amount of light that comes in and what your plants actually require.

What’s The Desired Phosphate Level For Aquariums?

As I mentioned, phosphate can be found in all tanks. You can eliminate it 100%. The optimal phosphate level to stop black mold and other algae growth is 0.2mg/L.

How To Lower Phosphate Levels In The Tank?

It is not an easy task to maintain the tank’s phosphate level. It is something you must work toward. You can make conscious efforts to eat less, perform water changes, and add algae-eating animals to your diet.

Feed your Fish Sparingly

Uncooked food can sink to the bottom of the tank and become a breeding ground. If you notice black molds, it is time to change your feeding habits.

Instead of eating one large meal, make small and frequent meals. Don’t forget about to throw away any unfinished food.

It is also important to consider the type of food that you are giving. Flake foods are often preservatived with phosphate.

But not all foods are the same. Before you buy any food, be sure to read the label carefully.

Reevaluate Your Water Source

This point has been explained in great detail before. Let me quickly recap: Tap water contains high levels of phosphate to prevent lead corrosion. You may need to change to distilled water or purified water by reverse osmosis if this is the case in your region.

These water types are depleted of important minerals, so you’ll need to remineralize them.

Perform Weekly Water Changes

In the hobby of fishkeeping, it is a good idea to do 20-25% water changes every week. While doing this, ensure that you are using phosphate-free waters.

The tank size and stocking numbers will also affect the frequency and extent of water changes.

Maintain Tank Health

It is a full-time job to maintain a fish tank. To maintain the tank’s health and cleanliness, you must be alert. Black mold can be prevented by keeping your tank clean.

Vacuum the bottom regularly to get rid of fish waste and other food that has gone bad.

Clean The Filter Often

Filters that are not cleaned regularly can hold enough phosphate and dirt to cause an increase in the tank’s phosphate levels. No matter what type of filter you use, it is best to clean your filter at least once a month.

The frequency of your filter is dependent on its capacity and your tank size.

Opt For Phosphate-Free Filter Media

Carbon is a great filter media and one of the most popular. It can also add phosphate. You can find carbon media that works as a phosphate absorber. This is a win/win situation for everyone.

Saltwater tanks, on the other hand don’t need to worry about this. The carbon media for saltwater tanks has been specifically designed to prevent phosphate from leaching into the water. Lucky!

Review The Conditioners

Many water conditioners contain phosphate, from those used to buffer water to those used for pH adjustment. The concentration of phosphorus varies from one product to the next.

Do your research before you spend.

Add Fast-Growing Floating Plants

Floating aquarium plants are very prolific and require a lot of nutrients in their water column. These plants require a lot food, and phosphate is one of them.

Here is a list of the best floating aquarium plants.

• Mosaic plant
• Water spangles
• Mosquito fern
• Water Sprite
• Red root floater
• Anacharis
• Dwarf water lettuce

Change Your Tank’s Bulbs

The light spectrum of bulbs gets less brighter as they age. Plants don’t get enough light to grow and photosynthesize, so they are less able to absorb as much. This light spectrum may be enough to allow algae to grow.

Algae will quickly take over the tank, as there are no plants to rival them.

Source Your Plants Carefully

Even decors and plants bought from reputable retailers could carry black moth. You should always disinfect them before you use them.

It sounds paranoid and germophobic, but hydrogen peroxide should be mixed with water in a ratio of 1 to 4. After letting the decors and plants soak for a few moments, it is best to let them air dry. Hydrogen peroxide does not leave any residue.

You can still clean them well before putting them in the tank. It’s better to be safe than sorry.

Add Algae Eaters In The Tank

Incorporating algae-eating fish is one of the best and most efficient ways to eliminate black molds from your tank. You cannot pick just a few random algae eaters.

It is important to consider their water requirements, dietary patterns and level of aggression first.

Fish That Will Eat Black Mold/Beard Algae

This is a complete list of invertebrates and fish that have been reported as eating black mold or beard alga (they are the exact same thing):

• Siamese alga eater
• American flagfish
• Twig catfish
• Rosy barb
• Cherry barb
• Chinese alga eater
• Bristlenose pleco
• Black molly
• Pigmy suckermouth
• Rubber-lipped pleco
• Flying Foxes
• Nerite snails
• Amano shrimp
• Goodeids
• Emerald crab

After hours of giggling through forums and blogs, I came up this list. We can’t be certain who will eat black mold, but we don’t know for sure.

It is more than just species. It also depends on the fishes’ personal preferences. Good luck!

If you are one of the fortunate ones who have fish that eat black molds you should still ensure they eat other nutritious, more filling foods.

It would be cruel to suppose they could survive on only algae.

Black Algae In Fish Tank – How To Get Rid Of It?

Black algae is actually called black beard algae. This is for obvious reasons. It grows almost exactly like a black fuzz, which is very similar to a human’s beard. Its growth and appearance in home aquariums is primarily due to phosphate. The best way to eliminate the algae is to reduce phosphate levels.

In fact, the black mold we have just mentioned is actually black beard alga in its highest stage!

We discussed the causes of the spike in the tank’s phosphate levels above. These include overfeeding, feeding phosphate-rich food, poor lighting and improper husbandry practices.

It can be very helpful to switch to RO or distilled waters, cut back on feeding, perform frequent water changes, and introduce black algae-eating species such as siamese algeater and Amano shrimps.

Final Words: Black Mold In Fish Tank

It was a long article. Just wanted to make sure you knew everything I know about this topic. If you don’t have time to read the entire article, here’s a summary of the key points.

Black Mold, also known as black beard algae, is a form of early stage black mold that looks like fuzzy, hairy and black patches.

It is not difficult to get rid of but it can come back to haunt your every day if you don’t address the root cause.

Black mold is caused by an increase in the tank’s levels of phosphate. There are many reasons why phosphate levels can rise, including overfeeding, poor lighting, buffers and carbon media, as well as lack of water changes.

You can tackle the phosphate spike and subsequent growth by changing your water frequently, using a water phosphate remover, switching from RO water to tap water, and feeding phosphate-free foods.