How to Use Avernus AlBlackEX Against Black Beard Algae

Black beard algae (BBA) is one of the most stubborn algae in planted aquariums. It grows as dark, brush-like tufts on wood, rocks, plant edges and equipment, and it rarely goes away on its own. This guide shows you, step by step, how to remove it with LGND Avernus AlBlackEX™ and how to stop it coming back.

What black beard algae looks like

BBA forms short, dense tufts that look like tiny black, dark grey or dark green paintbrushes. You will usually find it:

• on the edges of slow-growing leaves (Anubias, Java fern, Bucephalandra);
• on driftwood, rocks and stones;
• on filter inlets and outlets, hoses, glass edges and decorations.

Unlike soft green algae, BBA is rough to the touch and does not wipe off. If you rub it between your fingers and it feels like a stiff brush, it is almost certainly black beard algae.

Why it appears

• Too much organic waste: leftover food, fish waste and dead leaves.
• Irregular maintenance: too few water changes, dirty substrate or a clogged filter.
• Unstable CO₂ levels in planted tanks, especially when CO₂ goes up and down during the day.
• New plants carrying BBA spores: plants bought in pots or from other hobbyists can bring it in.

What you need

• LGND Avernus AlBlackEX™
• The 1 mL dosing syringe supplied with every bottle of Avernus AlBlackEX. You use it to measure the dose and to place the product exactly where it is needed.
• A bucket and a siphon or hose for lowering the water level
• A water conditioner such as LGND Priority™ for the fresh water you add back
• Optional: LGND Algae Master Brush™ for brushing away dead algae

How much to use

The rule is simple: 1 mL of Avernus AlBlackEX for every 40 litres of aquarium water, no more than once every 24 hours. The 1 mL syringe supplied with the bottle makes this easy: one full syringe is the daily dose for 40 litres. If you are not sure how much water your tank holds, use the volume printed on the box or in the manual.

PDFPrintable quick guideDosing table, step-by-step methods and a treatment log on 2 A4 pages. Print it and keep it next to your aquarium.Download PDF

Quick reference: common aquarium sizes

Aquarium volume	Maximum dose per 24 hours	With the 1 mL syringe
20 litres	0.5 mL	Half a syringe
40 litres	1 mL	1 full syringe
60 litres	1.5 mL	1½ syringes
100 litres	2.5 mL	2½ syringes
200 litres	5 mL	5 full syringes
300 litres	7.5 mL	7½ syringes

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Method 1: lower the water and treat (best results)

This is the most effective method for algae on rocks, wood and plants growing on hardscape. With the water lowered, the product sits directly on the algae instead of being diluted in the tank, so it works much better.

1. Switch off the filterAlso switch off the heater before the water level drops, so it is never left out of the water while it is hot.
2. Lower the water levelSiphon water out until the areas with algae are above the surface. Your fish stay in the water that remains, so there is no need to empty the tank completely.
3. Apply Avernus AlBlackEX with the 1 mL syringeFill the syringe supplied in the box and drip the product slowly onto the tufts, covering the algae. Stay within the daily maximum from the table above.
4. Wait a few minutesGive the product time to soak into the algae before the water comes back.
5. Refill the aquariumUse fresh water treated with LGND Priority™ (or your usual conditioner), at roughly the same temperature as the tank. Then switch the filter and heater back on.

Method 2: spot-treat plants in a full tank

Use this method for plants that cannot be exposed, or for treatments between water changes. You do not need to lower the water.

1. Switch off the filterStill water keeps the product on the algae instead of spreading it around the tank.
2. Apply with the 1 mL syringeHold the tip of the syringe very close to the algae and press slowly, so the product settles on the affected leaves.
3. Do a 50% water changeAfter treating, change about half of the water, then refill with treated fresh water.

Method 3: dose the whole tank

When BBA is spread across the aquarium, or after you have removed the visible tufts, you can add Avernus AlBlackEX directly into the water to deal with algae spores. Measure 1 mL per 40 litres with the supplied syringe, add it into an area with good water flow, and repeat once every 24 hours if needed.

Remember: if you spot-treat and dose the water on the same day, the total must stay within the daily maximum.

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After the treatment: refill and rebuild

1. Fill up the aquariumUse treated fresh water at the right temperature.
2. Switch the filter back onTurn the heater and CO₂ (if you use it) back on as normal.
3. Help the tank recoverAdd live bacteria such as LGND Entity™, a plant recovery supplement such as LGND Ancestral Phi™, and your usual fertilisers.
4. Repeat if neededYou can treat again every 24 hours until the algae is gone.

What you will see over the next few days

• Day 1–3: the tufts change colour, often turning pink or red, then pale or white.
• After that: the dead algae becomes soft. Many fish and shrimp will start eating it.
• Clean-up: brush the remains off wood and stone with the Algae Master Brush and siphon them out at your next water change.

The whole tank is affected? Fix the cause

If BBA is growing everywhere, Avernus AlBlackEX can help, but it cannot work alone. Algae grows because something in the tank is feeding it. For the next few weeks, follow this routine:

• Change 30% of the water twice a week.
• Vacuum the substrate at every water change and remove leftover food.
• Feed less. Depending on the number and size of your fish, feeding once every two days is often enough while you fight the algae.
• Use live plants instead of plastic ones. Live plants use up the nutrients that algae feeds on.
• Clean the filter every 3–4 months, rinsing the media in tank water from a water change, never under the tap.
• Keep spot-treating plants and decorations with Avernus AlBlackEX throughout this period.

Without this effort you cannot get rid of algae in general, not only BBA. With it, the treatment works faster and the algae has nothing to come back to.

Artificial plants and ornaments covered in algae?How to Use Plastic Plant & Ornament Cleaner→

Keep your plants well fed

Healthy, fast-growing plants are the best long-term protection against algae. Choose the fertiliser that suits your tank:

• LGND Essential™: natural growth supplement for roots and shoots
• LGND Heaven™: trace elements supplement
• LGND Avalon™: complete 2-in-1 supplement
• LGND Elysium™: 2-in-1 supplement, ideal for low-tech tanks

Stop BBA coming in with new plants

New plants are one of the most common ways BBA gets into a clean aquarium. Plants grown in vitro (in sealed cups of gel) are free of algae. Plants sold in pots, or bought from other hobbyists, can carry spores, so give them a short LGND Hades bath before planting. Our step-by-step guide shows the exact dilution, timing and rinsing.

Step-by-step guideBleaching Aquarium Plants with LGND Hades→

Frequently asked questions

Can I treat only the affected areas, or can I dose the whole aquarium?

Both. Treating the affected areas directly, with the water lowered, gives the best results. Dosing the whole aquarium (1 mL per 40 litres) helps against algae spores in the water. Just keep the total within 1 mL per 40 litres every 24 hours.

Is Avernus AlBlackEX safe for fish and shrimp?

Yes, when you follow the dosage on the label. The product biodegrades within 24 hours and is designed to be used in aquariums with fish and plants. Never exceed the recommended dose.

Do I need to buy a syringe or pipette?

No. Every bottle of Avernus AlBlackEX comes with a 1 mL dosing syringe. One full syringe is the daily dose for 40 litres of aquarium water, and the same syringe lets you apply the product precisely onto the algae.

How often can I treat?

Once every 24 hours. Keep treating daily until the algae changes colour, then remove the dead tufts.

Can new live plants bring BBA into my aquarium?

Yes. Plants from pots or from other aquariums can carry BBA spores. In-vitro plants are algae-free. For potted plants, give them a short LGND Hades bath before planting.

I replaced my live plants with plastic ones and still have BBA. What should I do?

Plastic plants do not use any nutrients, so they actually make it easier for algae to grow. Go back to live plants, follow the maintenance routine above and treat the affected areas with Avernus AlBlackEX. Any artificial decorations you keep can be cleaned with Plastic Plant & Ornament Cleaner.

How long until the algae disappears?

Treated tufts usually change colour within a few days. Heavy infestations can take a few weeks of daily treatment combined with good maintenance.

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Safety and storage

• Always follow the dosage instructions on the label and do not overdose.
• Store at room temperature, away from frost, heat and direct sunlight, in the original container.
• Keep out of the reach of children and pets.