Green Water Algae Profile and How to Remove

Green Water Algae Profile and How to Remove

The green water problem in freshwater aquariums is often caused by a bloom of microscopic green algae. Unlike Green spot algae (GSA) and Green dust algae (GSA), this green algae type is free-floating, and they do not settle on solid surfaces such as glass, décor, or aquarium equipment.

Green water algae make the tank unpleasant and inhibit visibility to a great extent, and that’s why it should be eliminated promptly. The good thing though is that it is easily preventable but if you still get it, it is not that hard to get rid of.

Now, let’s have a look at the description, common causes, and effective methods of removing green water algae in the tanks.

What is Green Water Algae?

Green Water Algae Profile and How to Remove from AquariumGreen water algae are a kind of microscopic (single-celled) green algae that turns the aquarium water hazy or murky green (Pea soup). They include planktonic green algae in the genera —Ankistrodesmus, Chlorella, Scenedesmus, and a host of others.

This kind of algae does not form crusts, patches, or coatings on the aquarium walls, surface of ornaments, and live plants rather it stays suspended on the water column resulting in a murky green water that is quite unsightly.

Initially, the multitude of microscopic green algae (phytoplankton) will turn the clear tank water into a slight hazy green color, and as they continue to grow and multiply, the tank water will gradually transit to a thick cloudy green water and the problem continues to worsen.

Green Water Algae Profile and How to Remove from AquariumThe aquarium water can get too murky, thus blocking out fish, décor, and equipment within the thick green fog formed. When there is a green water alga bloom in your aquarium i.e. a rapid increase in algae population within a short interval, it may create a situation where one can barely have a clear view of the interior of the tank, and the green algae could possibly block off artificial lighting from penetrating the tank water and getting to the plants.

Is Green Water Algae Dangerous to Shrimp, Fish and Plants?

Contrary to popular belief, green water algae are not detrimental to dwarf shrimp and fish in your aquarium. It doesn’t stop them from carrying out their usual activities. The interesting part is that many fish and shrimp species inhabit green colored ponds, swamps, and lakes in the wild.

Even though it is not very appealing to our eyes, basically, green water algae can be a sign that your tank has a natural balance.

Green Water Algae Profile and How to Remove from AquariumSo, they are not harmful to them in any way. On the contrary, in some cases, these algae can even be beneficial for the tank setups, because these algae will provide more natural food for the fry and baby shrimp.

Note: There are lots of microorganisms in our tanks that feed on the green water algae (phytoplankton), which in their turn are eaten by larger organisms, and eventually the fry and baby shrimp can feed on those organisms. As a result, they get a better survival rate and growth rate.

In addition, as with any type of algae, green water algae consume nutrients in your aquarium and by doing so it will make the water actually safer for your animals and that’s a good thing.

On the other hand, some plants may not suffer any harm from the green water algae, but as the problem gets severe, these algae will prevent light from reaching the plants thereby dwindling their growth.

Causes of Green Water Algae

1. Excessive Lighting:

There is no doubt that excessive lighting is the number one reason why people have green water algae.

Having too much light in the aquarium can lead to a green water algae bloom. Just like aquarium plants utilize light to carry out photosynthesis, so do algae.

The proliferation of green water algae is made a whole lot easier under the availability of excess lighting, hence leaving the aquarium lights on the whole day is a terrible practice. It is essential to maintain a standard photoperiod between 8-12 hours daily, and you have to be consistent.

Hence, make sure to regulate this using an aquarium timer; it presents an easy and automatic way to turn the lights on and off according to the user’s inputs.

Another thing to avoid is the usage of a light source that is too strong for your aquarium, one should stick to the recommended lights that can supply the required light output without ‘overheating’ the aquarium.

In the same vein, prevent direct sunlight from hitting the tank. Some hobbyists have a bad habit of placing their tanks close to the window (Read more about location tips here). Aquariums are more susceptible to an algae bloom when exposed to direct sunlight, and it is common knowledge that sunlight is a major requirement in green water culture for aquarists that breed daphnia and scuds.

Be sure to utilize only artificial light for your aquarium, since it’s way easier to regulate the amount of light that it emits.

Read more about light in my article “Advanced Guide to Planted Tank Lighting”.

2. Nutrient Imbalance:

The second reason for green water algae is a nutrient imbalance.

Ideally, in a planted tank, one is required to dose the right amount of nutrients to nourish the plants and keep them in good condition. That being said, having too much or less of the recommended values of CO2, nitrates, and phosphates can spell doom for your tank.

Similarly, the presence of too many fish or freshwater snails due to overstocking translates to the build-up of high organic wastes which tend to fuel the growth of green water algae.

Note: Unlike fish and snails, dwarf shrimp do not produce a lot of waste, thus overstocking should not be a problem at all.

The same thing goes for overfeeding, multiple bits of uneaten food in the tank accumulates nutrients that the algae feed off.

You can also read the article “How Often and How Much to Feed Shrimp”.

3. Poor Maintenance Practices:

When an aquarium owner fails to carry out routine maintenance practices, poor water quality and proliferation of algae is inevitable.

It’s necessary to clean the aquarium regularly and ensure weekly or bi-weekly water changes to avert the build-up of excess nutrients that encourage green water algae blooms.

How to Remove Green Water Algae

In general, it is about finding a balance in your tank. Ideally, you need to figure out what is the cause of your situation and act accordingly.

Nonetheless, there are also some ways that can help you to remove green water algae.

1. UV Sterilizer:

UV Sterilizer Uses and Purposes in Aquariums types This is beneficial aquarium equipment, it is very effective at killing off microbes such as bacteria, virus, and most especially phytoplankton that can cause green aquarium water. This equipment is safe for fish, inverts, and live plants; so you don’t have to worry about any adverse effects.

Once installed, aquarium water will flow through the UV chamber of the device, exposing it to ultraviolet light and the floating algae get radiated. After some days, the green aquarium water will change to a clear, transparent state.

Give it 7 – 10 days you will not have green water algae in your tank.

UV sterilizers are available in different sizes and models suited for a variety of tanks.

Read more about it in my article “UV Sterilizer Uses and Purposes in Aquarium”.

2. Fast Growing Plants

Water Wisteria (Hygrophila difformis, Synnema triflorum)Fast-growing plants help against green water algae because they easily compete and outcompete algae for the nutrients (like nitrates and phosphates) from the tank water.

Remember: if plants do not grow fast enough, they do not eliminate ‘mineral leftovers’ in the tank, so, it allows algae to boom.

What plants are the best for this job?

Ideally, these plants should meet 2 criteria:

Another great thing is that floating plants prevent algae from getting light!

How fast can plants remove green water algae?

In most cases, under optimal conditions, it may require a week or so.

3. Block Light Completely:

Since excess light fuels green water algae blooms, think of what will happen in the absence of light. Well, you guessed right…the algae population will not be able to photosynthesize further, hence resulting in a gradual die-off. Here’s how you can achieve that.

How to do a Blackout:

  1. If you have fish, feed them a regular amount of food. Do not overfeed. If it is a shrimp tank, you may even skip this step.
  2. Turn off the CO2 if you run one.
  3. Do not add any plant fertilizers during the blackout.
  4. Increase the oxygen supply. Install a new air-pump if needed.
  5. Wrap the tank with dark cardboard, cloth, or anything similar. It must be completely dark in the tank.
  6. Leave the tank this way for at least 3 days. Some aquarists recommend 5 days.
  7. Open up half of the tank and leave like this for 30 minutes. Let your fish adapt.
  8. Remove the blanket completely and wait another 30 minutes before switching the aquarium light on.
  9. Clean equipment as the dead BBA can clog it easily.
  10. Do a water change to get rid of a huge bioload all you suddenly get in the tank. The point is that dead algae in the water column can cause ammonia spikes. So, if it is a fish tank, it can be a 50% water change. If it is a shrimp tank, do a 10 – 15 % water change. Large water changes affect shrimp molting.
  11. Change your light timer to 4 – 5 hours for the next week.

Note: Monitor the situation at intervals! If you decide to feed your animals, you can uncover the tank to feed the inhabitants, after which you should cover it up again. Whenever it is possible do not turn on the lights even briefly.

Important: During this period, the tank should be properly aerated using an additional powerhead or other aeration devices. Put a temporary halt on the addition of CO2 and liquid fertilizers, and feed the inhabitants sparingly. Furthermore, make sure to observe the state of your tank inhabitants and live plants intermittently throughout this period.

The plants may get leggy during the black-out period, but they will gradually bounce back to normal health as soon as lighting is restored.

4. Diatomic filter:

Diatomic filter - Green Water Algae Profile and How to RemoveThis is another good method of eliminating green water algae in an aquarium. The diatomic filter utilizes diatomaceous earth to trap microscopic particles which include suspended algae in the water column.

According to the manufacturer Vortex Diatom:
“The “Diatom” is a high speed auxiliary filter designed to filter aquarium water to an extremely pure state. The Diatom Filter is extremely fast and will filter out particles as small as one micron (one millionth of a meter). 

Keep in mind that they are NOT meant to be used 24/7 as common aquarium filters.

Vortex XL Diatom Filter – link to check the price on Amazon

5. Daphnia:

How to Culture Daphnia in AquariumsAlternatively, one can as well get the green water algae condition under control by introducing Daphnia (water fleas) — small crustaceans that will gladly devour the phytoplankton that is turning the water murky green.

It is a natural and inexpensive way of eradicating green water algae in the aquarium. The presence of sufficient quantities of Daphnia in the tank will reduce the algae significantly, and in turn, they will serve as a delicacy for aquarium fish.

You can also read “How to Culture Daphnia in Aquariums”.

Note: Vampire shrimp and Bamboo shrimp can also eat Gren water algae. Due to their unique food intake technique, they can easily eat free-floating algae and microorganisms. However, do not expect them to clean your tank.

6. Chemical Treatment:

The use of chemical substances (algaecides) to cure green water algae problems should be a last resort, the reason being that one can’t control the adverse effects of chemicals on fish, inverts, live plants, and the overall health of the aquarium.

They will only eradicate green water algae blooms without actually solving the cause of the problem. In addition, the use of chemicals can result in depletion of oxygen levels, so it’s best to consider other methods.

Nonetheless, if you still want to use chemicals to deal with green water algae, these are some of the products.


API algaefix vs hair algaeAlgaeFIX is very effective against green water algae.

Unfortunately, this product is not safe for invertebrates including shrimp, snails, crayfish, etc.

Even more, in spite of the description that it “controls many types of algae in aquariums and will not harm to your fish or plants when used as directed”. There also some complaints that AlgaeFix also killed fish, even when dosed according to the bottle.

That is why aquarists often use it for dips only and use it as a full tank treatment only in desperate situations. Personally, I would start with ½ (or even less) manufacturer’s recommended dosage.

AlgaeFIX – check out the price on Amazon

Ways to Prevent Proliferation of Green Water Algae

  • Do not overfeed.
  • Do not overstock.
  • Regular water changes.
  • Removal of uneaten fish food and periodic vacuuming of the aquarium substrate.
  • Prompt replacement of the filter cartridges and filter media when necessary.
  • Maintaining proper stocking and feeding to prevent excess waste.
  • Regular testing of the tank water using an accurate aquarium test kit to ensure that the water parameters are at the appropriate levels.
  • Avoid placing the tank under direct sunlight.
  • Use an artificial light source that suits your tank needs, and maintain photoperiod between 8-12 hours daily.

In Conclusion

The outbreak of green water algae in your aquarium is not something you should lose sleep over, though it can simply be prevented by adhering to proper tank maintenance habits and ethics such as performing regular water changes, cleaning the aquarium gravel, keeping to the right stocking/feeding and using the proper light source for your aquarium.

However, if your tank is already suffering from a green water algae bloom, then you need to promptly make use of the solutions to put an end to it. The methods outlined are all effective, and some can even be used in combination to proffer a quick fix to the problem.

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