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the truth about green spot algae ultimate guide 2022

green spot algae in aquarium
green spot algae in an aquarium

What is the green spot algae ?

  • It’s a green, small and circular spot that is where its name came from. This kind of algae doesn’t grow tall like other kinds. It is almost flat and hard to touch.
  • This algae grows on the substrate, rocks, driftwood, and even the glass of your aquarium. So you can say it grows on objects that don’t move. Consider if you have plants in your aquarium and they grow slowly then you will find dark green spots on it.
  • Most people first notice the spots on the glass of their aquarium since it blocks their view.On the glass of the aquarium, the green spots look a lighter shade of green. This is because the light hits the algae from both sides, making it appear lighter.
  • Pair in mind that green spot algae are harmless to your fish, but it can harm your plants but only if you let it completely cover your plants, therefore the green spot algae on plants will eventually block any light from reaching to plants. And as we all know, plants need light for energy.

What causes green spot algae to appear?

  • a nutrient imbalance is a cause. Many experts agree that too much light and Low phosphate levels play the biggest role in the appearance of green spot algae on plants
  • High levels of light, either from a nearby window or from your aquarium light, can be responsible for green spot algae. Fixing your light levels is the easiest way to prevent it from appearing in your aquarium. You can reduce how long your aquarium lights stay on by using a reliable plug-in aquarium timer.
  • Now you should test the level of phosphate in the water of the aquarium using an aquarium test kit. If your phosphate levels are near zero, then it’s likely that this is the cause of your algae. Don’t expect the green spot algae will disappear at the moment that you add phosphates. It’s a slow process and may take weeks before it begins to recede.

How to get rid of green spot algae?

You can get rid of green spot algae either manually or using algae eaters.

Manually: you should scrap the glass of your aquarium using simple stuff such as a strong plastic card. Stick with this position, Angle the used plastic card and slide it down the glass of your aquarium, you should see the green spot algae lift off.

Keep rubbing until you have removed all visible signs of green spot algae from your aquarium glass. Once done, use the water to help remove any gunk that you scraped into the aquarium.

green spot algae on plants
green spot algae

Algae eaters: Algae Eaters are often used by professional Aquascaper including sun snails or species of nerite snails. These hungry snails have an appetite for green spot algae. Whether it’s on your glass, plants, driftwood, or rocks, they will hunt it down and eat it up. Pair in mind If you let your  problem grow out of control, you may need multiple Snails of algae eaters.

How To Prevent Green Spot Algae Appearing back?

increasing levels of phosphates in Aquarium by adding phosphate monobasic potassium, increasing levels of dissolved CO2 as well as improving the system circulation. The use of magnetic glass can also help prevent algae reappear at the surface of the glass. Increasing the intensity of the lighting to 9-10 hours per day until the State of the aquarium is back to normal.

The other most common types of aquarium algae

1. Brown Diatom Algae :

  • looks like a dusty, flour-like substance covering your aquarium walls, substrate, and other surfaces. Because it’s so soft, it easily scrubs off, and many animals like to eat it. Brown algae isn’t actually algae at all.
  • It’s made up of little single-celled organisms called diatoms.
  • Diatom algae are most commonly seen in newly planted tanks normally, a few weeks after a tank starts to cycle, diatoms start to appear in the tank. and is often caused by high levels of phosphates and silicates.
  • It’s one of the simplest algae to get rid of because if you just give it some time, the plants will naturally consume the extra phosphates and silicates.
  • To get rid of it you should perform water changes. Doing frequent water changes is one of the best ways to help remove brown algae.
  • When you do change out the water, it removes the nitrates and phosphates that the brown algae eat.
  • Make sure to really get down in the substrate with a gravel vacuum. Fish waste falls down to the tank floor and sinks into the gravel. All that waste constantly puts off nitrate and phosphate. Getting it out of the tank helps to starve out the diatoms.

To prevent them from coming back :

  • Increasing filtration can really keep brown algae gone.
  • Keep up the water changing.
  • Increase water flow, Brown algae really doesn’t like high water flow.
  • Avoid silicates
  • Avoid overfeeding, You should only feed your fish what they can eat in about 30 seconds
  • Use chemical filtration, There are several chemical filtrations that can help remove silica, nitrate, and phosphate from your tank water.

2. Black Beard Algae :

one of the hardest algae that people run into because there are not many things to eat. It grows in very thick, bushy clumps that are usually black or grey in color. This algae likes to grow on driftwood, aquarium decor, and plants, and if left unchecked, it can completely damage an aquarium in one to two years. While black beard algae are considered to be saltwater algae, there are strains that are common to freshwater tanks. Despite what we mentioned about this algae it is not dangerous to your fish but it is harmful to the plants if you have it in your aquarium.

Let we see the causes of black beard algae:

  • CO2 fluctuations, If your CO2 levels are too low, your CO2 is fluctuating or you have poor water circulation, you are creating an environment that is perfect for black beard algae to grow.
  • Much light, black beard algae-like light. The more light it has, the faster it spreads into your aquarium. This is a particular problem for people who have plants in their aquarium, using LED to grow the plants but isn’t just helping their plants to grow but algae too.

In order to remove black beard algae, you should fix the cause not scraping them like green algae. So you can try :

  • Cutting them, This solution will only work if black beard algae have just begun to appear in small numbers on your plants
  • Liquid carbon, is amazing for planted tanks! Not only because the black beard algae hate it, but also it will improve the growth of the other plants in your aquarium.
  • Black beard algae eaters, you can use this fish that is called Siamese algae eater.

3. Hair Algae :

  • These algae grow in a huge amount on the surface of the aquarium, therefore it will cut out the light and it may kill the fish too. So this algae is considered a disaster for all people who have any kind of aquarium. Whenever you see these algae you have to remove them from your tank before they take over the whole tank and this will turn your tank into a jungle and it will be hard to get rid of them.

  • Hair algae grow more with the help of phosphate and nitrate. Therefore, when the levels of phosphate and nitrates are high there is a high possibility that hair algae will appear in your tank.
  • Another reason for the hair algae to appear in your tank is the light, especially when the light in your tank is too bright then hair algae will spread even faster. Finally, Co2 can also cause hair algae, a perfect level of CO2 in the tank should be 20-30 ml per liters.

 There are different ways to get rid of this algae :
1- you can get rid of it by ripping it, you have to rip the hair algae from the tank wall and from the rocks if  there are. But while you doing that you have to make sure that the filter is turned off.

2- you need to lower the level of the phosphate and nitrates, The level of phosphate should be .05 ml per liter and the level of nitrate should be 10ml per liter.

3- also  you need to lower the level of the brightness in your tank

4- you can get help by hair algae eaters such as Ameca splendens, flagfish  Jordanella floridae, mollies or other algae eaters, and ghost shrimps 

5- finally, plants and water changing. The regular water changing can low the 
        chance of existing and growing the hair algae in your tank


Summary: Green spot algae is named for what it looks like. It is small, circular green spots.  commonly grow on objects that don’t move such as substrate, rocks, driftwood, and even the glass of the aquarium. If your plants grow slowly this may cause the green spot algae aquarium to start appearing in your tank.

In its early stages, these algae appear as isolated spots. If you are not looking for it, it can easily be missed. Most people first notice the spots on the glass of their aquarium since it blocks their view.
Although it may make your tank looks ugly it is harmless to the inhabitants of the tank    

We mentioned that what green spot algae causes is :

  • Too much light.
  • Low phosphate levels
  • Poor plants inside the aquarium

And to remove them you can use :

  • Manual removal.
  • Algae eaters
  • Regular water changing
Although all that we mentioned about green spot algae but Some people allow it to accumulate in their aquarium because they like the look of it after this much information, let us know what are your successful experiences through the comment fish tank 360
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