6 Best Methods For Getting Rid Of Green Spot Algae In The Planted Aquarium

In this article, we will concentrate on Green Spot Algae (GSA). They often appear in the planted tank as a bunch of little green dots sticking to hard surfaces. It includes hardscape, aquarium equipment, substrates, ornaments, and aquatic plants with slow-growing leaves.

As with other freshwater aquarium algae, they can be a nuisance and can be fairly nasty in your aquarium. This is because their tendency to form ugly green coats on the fish tank makes it unattractive and, in some cases, uncomfortable for aquatic creatures.

In the beginning, you can still tolerate their presence because there are so few of them, so you are not too annoyed. However, if these algae grow out of control, they will cover any aquarium objects. In this case, they will not appear as tiny dots but as green coats over the surfaces.

What Is Green Spot Algae?

Green spot algae (GSA) is a member of the freshwater aquatic green algae family. They belong to coleochaete, which is a genus of parenchymatous charophyte green algae under the Coleochaetales order.

These algae types can attach to various surfaces in the aquarium, including plants, decorations, equipment, substrate, and even the wall glass.

GSA’s growth is quite swift under favorable conditions. It can quickly establish in a hardscape and, within a short time, spread to nearby objects in the planted aquarium. Then, if you are untreated, they will cover the entire area for several days.

How To Identify Green Spot Algae In Freshwater Aquariums

You can easily identify these algae from their shape. They are present in the aquarium as little circulars with bright green. They often appear as colonization of numerous green dots, then grow to creep up to the closest objects. You can feel their texture when you run your fingertips over them.

Generally, they establish small green spots on hard surfaces, such as wood, stones, and tank glass. GSA also frequently develops on the leaves of slow-growing aquatic plants such as bucephalandra and anubias species.

The green spot algae that form on the wall glass usually has a lighter green tint. Meanwhile, those that vegetate on the plants’ leaves naturally arise as slightly dark green dots.

Their size is tiny, about 1 millimeter (0.004 inches) in diameter. However, when you left them to grow up without any way to control them, they would merge and become a blotchy mat on the object’s surface. Well, at this phase, they may not seem like spots anymore.

Another fact about green spot algae is that their growth rates are slow. They differ from most aquarium algae, which typically multiply rapidly.

How Does Green Spot Algae Reproduce?

Green spot algae are haploid; they reproduce both asexually and sexually. This alga also exhibits true multicellular organization, with plasmodesmata facilitating communication between adjacent cells.

• The asexual reproduction process occurs by the formation of zoospores.
• The sexual reproduction method happens by oogamy. Once fertilization is complete, the sterile jacket of cells will form and then surround the zygotes for their protection.

Green Dust Algae VS Green Spot Algae

There is another green alga that is almost similar to GSA when present in the aquarium. Green dust algae (GDA) can form green flat coats on the surfaces of aquarium objects, similar to green spot algae.

Both of them typically grow on the leaves and decorations in the fish tank; they will continue to reproduce, making their population grow larger if the conditions are favorable.

However, when you look at their morphological features, you will see that they are actually different from each other. As their name suggests, green dust algae form dust-like layers of green on walls, glass, and aquarium surfaces. In comparison, the green spot algae appear as tiny, thin, circular disks on the surfaces.

You can use your fingertips to feel their texture to differentiate these two green algae types. The green spot algae give a rough or harder sensation on the edge of your finger when touching them, while the green dust algae are relatively smooth and easy to lift off.

The second point about them is that GSA is difficult to wipe off surfaces; green dust algae can be scrubbed off or removed easily. Nonetheless, if you let them thrive without being treated for an extended period, the GDA may also develop a thick, green film that is difficult to scrape off.

Third, the growth rate of green spot algae is slower than that of green dust algae. Lastly, GDA has a light green color, which is different from the GSA, which is slightly darker.

Generally, green dust algae are caused by abrupt changes in the aquarium, such as fluctuations in parameters, excessive light intensity, changes in equipment, or the addition of new pets. Treating GDA is slightly simple: make some water changes and keep the aquarium parameters consistently stable.

What Causes Green Spot Algae In The Freshwater Aquarium?

This freshwater aquarium algae can be triggered by several factors, including a deficiency of carbon dioxide, overlighting, low or too high phosphate levels, high organic waste, and old, damaged leaves. These elements collaborate to push the development of green spot algae in the aquarium.

Carbon dioxide deficiency: a lower CO2 level in the water is a major reason that stimulates most aquarium algae to bloom, including this green spot algae.

Excessive lighting: An aquascape tank with high lighting intensity and long photoperiods is prone to infection by the green spot algae plague. This condition is a perfect opportunity for them to grow, especially if it combines with other unfavorable factors, such as lower CO2 levels, which will lead to larger numbers of green spot algae.

Higher or lower nutrients: in principle, the unstable necessary nutrient content, like phosphate, is a great way for the GSA to bloom. Thus, as an aquarist, you should give proper doses of nutrient fertilizer into the water of the aquarium.

High organic waste: a high infestation of decomposed plant matter and fish feces in the aquarium can cause green spot algae to thrive. This alga also often appears on the old, damaged leaves of plants. Some aquatic creatures, like ramshorn snails, can have a significant impact on organic waste production due to their rapid and prolific breeding, which is why a few tank keepers often ban them.

Another factor that can influence them to live is weak water flow. Poor water circulation causes detritus to accumulate in certain areas of the planted tank, making it fertile ground for algae to grow.

Are Green Spot Algae Harmful to Aquatic Plants In The Planted Tank?

It is still normal if your tank has a small population of green spot algae. Most planted aquariums have experienced algae outbreaks. They are not dangerous to your valued aquatic plants as long as their growth can be handled.

However, as contamination worsens, this alga can significantly damage plants. The green spot algae would compete more for nutrients in the water; clearly, this would stunt their growth.

Besides, when green spot algae spread widely, they cover most of the plants, preventing them from photosynthesizing and growing. In this worst condition, the aquatic plants would be dying slowly.

Are Green Spot Algae Harmful to Aquarium Fish?

Actually, green spot algae are safe for fish and other aquarium creatures. Unfortunately, only a few fish species are willing to munch on this alga type, and most of them tend to be uninterested due to their harsh texture.

However, some aquarium algae-eating snails readily accept these algae as their extra snacks in the tank. If you do not take any action against them, they will multiply, wrap the plants, and prevent them from producing oxygen. It decreases the O2 level in the water, making it hard for your fish to breathe; in the worst case, they may die.

How To Remove Green Spot Algae In The Aquarium

In order to treat and stop green spot algae growth in the planted tank, you could follow the steps below:

Manual Removal

This method helps reduce the green spot algae population; however, it cannot wipe them out entirely. This method is effortless; however, you will need special tools to scrape or scrub them on the surfaces. Below are some samples that are usually sold on Amazon; choose one that fits your problems:

• Toothbrush
• Blades
• Algae scrapers
• Magnetic algae scrubbers
• Scrubbing pads
• Glass cleaning scrapers

Suppose you have an aquarium made of acrylic. You should use certain tools or blades that would not leave scratch marks on the walls of your tank.

The manual cleaning method helps eradicate algae from the tank glass, ornaments, and equipment. Scrape these objects gently until no visible traces of green spot algae remain in the aquarium. Use a gravel cleaner or a spade to remove the algae coating on the substrate, along with the detritus.

How do we get rid of green spot algae from the plants? The proper way to remove them from the aquatic vegetation is to cut off the infected leaves or parts and dispose of them outside the tank. Remember, these algae are stubborn, which means it is not possible to kill out the green spot algae without hurting the plants, so take your scissors and prune them off.

How to get rid of green spot algae on the decorations and equipment? It is straightforward: remove the rocks, driftwood, aquarium gear, and other debris. Then, scrub the surface with an old toothbrush, rough sponge, or scouring pads under running tap water.

Introducing Green Spot Algae Eaters Into Your Infected Planted Tank

Adding algae-eating crews can reduce the growth rate of green spot algae, but the effect depends on outbreak levels. They are effective against low to medium-sized cases. Several fish species that usually munch on this alga, including:

• Borneo sucker fish
• Otocinclus catfish
• Royal farlowella
• Chinese hillstream butterfly loach
• Garra rufa
• Siamese algae eater

Compared with other aquarium shrimp species, Amano shrimp are more likely to eat green spot algae, although they tend to ignore algae that form on the glass wall.

Do nerite snails eat green spot algae?

Nerite snails are an excellent weapon for killing green spot algae. But they need a long time to grow; this gives the algae a chance to replace themselves after they are swallowed. You may require more nerite snails to anticipate this problem; however, it can lead to another issue, like an infestation of organic waste produced by the snails. Make sure to clean your tank frequently while performing this treatment method.

How many nerite snails do you need?

It depends on how big your tank is and the algae population. If you buy snails to control algae growth, you generally need 1 snail per 20 liters of water (5 gallons).

But if you keep them to devour many tough green coats, at least add two or more nerite snails for five gallons of water, depending on the tank condition. In the end, you will see the difference in your aquarium, but do not make a wish for a quick result.

Aside from nerite snails, there are a few aquarium mollusk species that have a similar ability to wipe out these algae, preferably, including:

• Theodexus snail
• Hairy snail
• Japanese trapdoor snail
• Mystery snail
• Rabbit snail
• Ramshorn snail

Phosphate Dosing Treatment

A nutrient deficiency, primarily phosphate, is the main cause of green spot algae in the fish tank.

Insufficient nutrition leaves plant health in a very poor state. They should also constantly compete with algae for food resources in the water, making their condition very poor.

Before you perform this treatment, check the dissolved nutrient content using your favorite aquarium test kits.

Accordingly, to resolve these algae problems in your freshwater aquarium, increasing the phosphate level as required is a good step to eliminate them. The recommended phosphate range is 0.05-1.5 mg/L, which supports the growth of aquatic plants and minimizes algal growth.

Then, it further needs a nutrient dose (especially phosphate content) to be slightly in excess throughout the week. Lastly, perform a 50% water change at the end of the week.

Another way is to inject potassium phosphate directly into the green spot algae zones within the planted aquarium.

• Firstly, prepare the dry potassium phosphate powder (KH2PO4) and a syringe or pipette.
• Next, add some phosphate powder to the syringe/pipette, mix it with a small amount of water, and shake it.
• After that, turn off the aquarium filter.
• Apply this solution to the objects where green spot algae exist.
• Leave it to work for up to 5 minutes, then turn the filtration system back on.

Do not let the phosphate level exceed your tank’s tolerance, as it can lead to another issue. If this happens, the water’s nutrient levels become too high, and your plants cannot absorb them all. To prevent this from happening, you should perform a water change.

Keep in mind, if you keep a shrimptank, huge and/or frequent water changes may cause molting issues for your crustacean pets. Well, be careful with that.

Carbon Dioxide Treatment

It is essential to install a CO2 checker to easily monitor CO2 levels. If your freshwater fish tank lacks CO2, boost the CO2 content to a specific level by installing a carbon dioxide injection system (if you do not use a CO2 kit). Once the green spot algae population has decreased significantly, gradually reduce the CO2 rate until it reaches the normal level.

Does Seachem Flourish Excel Eradicate Green Spot Algae?

Some aquarium hobbyists like using a carbon liquid from the seachem brand called Flourish Excel to get rid of most aquarium algae types. This popular product has been proven to help aquarists inhibit algae growth due to its glutaraldehyde content.

Flourish Excel is a popular commercial aquarium product that supplies organic carbon to the water. This can substitute for dissolved CO2 because the carbon content can still be used and absorbed easily by aquatic plants for photosynthesis.

Most aquarium algae can be killed with this solution, such as:

• Green dust algae
• Green Hair Algae ( such as Spirogyra, Rhizoclonium, Oedogonium, and Cladophora)
• Brown algae
• Black beard algae
• Staghorn algae
• Fuzz algae

How to use Seachem Flourish Excel to kill the green spot algae

Simply take a small dose of this solution directly through the syringe into the algae clusters. Use a 3- to 5-mL dose of Flourish Excel every day until the algae are gone. This product is safe for your fish, shrimp, and snails, and the plants will be happier with the increased carbon content.

A different, similarly powerful product to Seachem Flourish Excel is API Algaefix. Both of these cures can help remedy your tropical tank from most types of aquatic algae that often invade the aquarium.

Green Spot Algae Chemical Remover

Chemical removal treatment is the last method to destroy this pest. This product is effective for high outbreak levels and eliminates the remaining debris that cannot be scrubbed off. You can buy a hydrogen peroxide or bleach solution at nearby stores. However, we do not recommend this solution because it may damage your tank; remember, these chemicals are harmful to your aquarium’s inhabitants.

Take this medication twice at specific times, and do not forget to wear gloves during treatment. H2O2 and bleach are also helpful for disinfecting and quarantining new or old infected aquatic plants to remove fungus, bacteria, algae, and other creatures that can be parasites (such as planaria, scuds, and hydra) in the planted aquarium.

To make a cleaner mixture, use 20 parts water to 1 part bleach (20:1) in a suitable vessel; do not forget to remove the lousy component first.

• Use tweezers to soak the plants or equipment in order to avoid direct contact with your skin.
• Leave them submerged in the mixture for 5 to 15 minutes.
• Once the algae get noticeably brighter, move the plants into a container with clear water.
• Add some water conditioner to the water container to neutralize the chlorine, then rinse the plants or equipment with running water until they are completely clean.

Now, we will talk about how to get rid of the green spot algae inside the aquarium:

• Use 3% hydrogen peroxide.
• Move all aquarium populations, including plants and pets, into a separate tank. Ensure that you quarantine the aquatic plants to remove the green spot algae that adheres to them.
• Discard the filter media from the filtration system to save the beneficial bacteria. Place it in a box or container filled with cycled water and oxygenate it with an air stone during the medication process.
• Add 25-35 ml of 3% hydrogen peroxide per 50 liters of water, depending on the condition.
• Pour this solution into the water surface, then stir it gently until it spreads completely. Leave it in the tank for 2 to 3 hours while the filter continues to run to maximize the treatment effect.
• Release and refill your aquarium with new freshwater at least 3 times to remove any remaining hydrogen peroxide and algae.

After completing these treatment steps, you can introduce your livestock and aquatic plants, and then reinstall the filter media into the filtration system.

How To Prevent Your Fish Tank From Green Spot Algae Invasion

Prevention is the best practice rather than medication. Well, doing some activity that can keep your aquascape tank from green spot algae is necessary, such as the following:

• Keep the water parameters and nutrients in the fish tank consistently stable by regularly checking them with the tester.
• Perform regular water changes and tank maintenance.
• Never overfeed your livestock.
• Nurture some algae eaters in your fish tank to control algae growth.
• Address livestock and plant health issues as quickly as possible in a different location.
• The average reasonable lighting period is 7-8 hours; a photoperiod shorter than this can cause your aquatic plants to underperform, and a lighting period longer than this may trigger other problems, such as staghorn or brown algae.