Algae Management and Algae Myths in the Planted Aquarium

Algae Management and Algae Myths in the Planted Aquarium

Algae management is often one of the most difficult and irritating aspects of the planted aquarium hobby. Without the right management, it is easy for algae blooms to get out of hand, which often leads to a ruined aesthetic and algae-smothered plants. Such issues can often lead to frustration and quitting the hobby altogether. This guide is intended to help aquarists to manage algae specifically within the context of a planted aquarium, which is a unique type of system in its own respect.

Managing algae within a planted aquarium is much different than managing algae in ponds, lakes, or other naturally occurring ecosystems. Hence, many of the traditional algae management strategies such as limiting Nitrogen or Phosphorus simply do not apply to the planted aquarium, since they are fundamentally different systems.

What Makes a Planted Tank Unique?
A planted tank is unique for two main reasons: it is often plant dominated and is a closed system. That is, aquatic plant biomass makes up the majority of the biomass within the system, and there is limited transfer of matter in or out of the system. While it may seem obvious that planted tanks are plant dominant, it is important to realize that many natural aquatic ecosystems are not dominated in biomass by aquatic plants.

For instance, a lake may have aquatic plants in it, but most lakes only have habitable areas for aquatic plants on the shores of the lake. Plants cannot grow in all areas of the lakes since the light penetration into deeper water is limited. However, if we look at the typical planted aquarium, we typically see that a vast majority of the surface area within the tank is covered with aquatic plant mass. This is not typical in nature. Additionally, a lake is an open system. It is constantly being fed new water through other waterways and rain, and loses water through evaporation and other waterways. There is a constant movement of water through the system, which can supply nutrients and remove wastes while keeping water parameters relatively stable. Most planted aquariums are a closed system, so the only water movement that occurs is through water changes.

What Causes Algae?
At the core of the issue, poor plant health causes algae. In a plant-dominated system, algae will only be able to thrive when the dominant organism (the plants) are failing in some sort of capacity. Algae is opportunistic and will often grow on plants that are weakened or are actively decaying. This is because the dying plants release organic matter as it decomposes, which is an easy source of food for the algae. Theories of allelopathy and competition have been proposed as mechanisms to explain how plants suppress algae growth within the planted aquarium. While the mechanisms in play is a bit irrelevant to the discussion, the key takeaway is that poor plant health = algae.

So why are the plants in poor health? That can be due to a variety of reasons. Here are some of the most common causes ranked in no particular order of importance.

  1. The plants aren’t getting the nutrition they need. Plants need all macro and micro nutrients in sufficient quantities. If they do not receive all necessary nutrients, it leads to nutrient deficiencies. Nutritional deficiencies lead to weakened plants, which then decay and give the algae a perfect place to grow on.
  2. The plants aren’t getting sufficient light, or a proper light source. Plants need a light source to grow that has the correct spectrum. Seeing as light is the driver of photosynthesis, is it extremely important to have a good quality light to give your plants a fighting chance.
  3. The plants aren’t getting enough carbon dioxide, or have an unstable source of carbon dioxide. This is especially relevant in high tech aquariums with injected CO2. With injected CO2, it is important to ensure that your bubble count is stable/consistent throughout the day and that you are injecting enough CO2 into the water to match your light level. Lowtech aquariums typically do not have this issue as the CO2 levels remain fairly constant.
  4. The tank is dirty and filled with ammonia & organic detritus/waste. A tank with tons of waste does not create an optimal environment for plant growth, which can lead to weakening of the plants.
  5. The aquarist practices poor plant husbandry skills. It is possible that the aquarist does too little/too much trimming, doesn’t maintain the substrate, doesn’t maintain equipment properly, or fails to provide particular species with what they need to succeed.
  6. Your plants are stressed out. Your fish may be picking on them, they might be transitioning from their emersed to submersed state, they may be fresh out of a shipment, or there is some other factor that is causing them to be stressed.

Treating Algae: Understanding Elements of an Algae-Free Aquarium
Typically, there is not a “one shot” solution when it comes to dealing with algae. Most algae issues are the result of many ongoing issues, which are unique to a particular aquarium. For most scenarios, it is impossible to give a one-solution-fixes-all type of remedy. Rather, it is imperative that the aquarist identifies the problem(s) within their own aquarium and takes the correct step(s) to address the problem. However, it is very helpful to understand the elements and behind-the-scenes work of an algae free aquarium so that these same elements can be applied to personal aquariums. I will provide examples below of various setups I’ve created which are algae-free.

Tank #1: Hightech 20G Long
Lighting: SB Reef (extremely high light)
CO2: Pressurized system injected through inline diffuser
Fertilizer: Custom dry fert schedule that contains all essential nutrients dosed daily
Substrate: UNS Controsoil (Nutrient rich aquasoil)
Filtration: Oversized Canister filter cleaned every two months
Plants: Variety of intermediate stem plants
Maintenance: 75% weekly water change and 1 hour trimming session every other week. Tank was kept extremely clean with minimal organic waste buildup.


Tank #2: Hightech Nano Aquarium
Lighting: ONF Flat Nano 100% Intensity
CO2: Pressurized system injected through ceramic atomizer
Fertilizer: APT Complete (all-in-one fertilizer containing all essential nutrients) dosed four times a week
Substrate: Mineralized topsoil capped with UNS Controsoil (nutrient rich substrate)
Filtration: None
Plants: Easy stem plants and carpeting plants
Maintenance: 90% weekly water change and 30 minute trimming session every 3 weeks. Tank was kept extremely clean with minimal organic waste buildup.


Tank #3: Lowtech Nano Aquarium
Lighting: ONF Flat Nano 50% Intensity
CO2: None
Fertilizer: APT Complete (all-in-one fertilizer containing all essential nutrients) dosed twice a week
Substrate: UNS Controsoil (Nutrient rich aquasoil)
Filtration: None
Maintenance: 50% weekly water change and 30 minute trimming session once every 6 weeks. Tank was kept extremely clean with minimal organic waste buildup.


Tank #4: Lowtech 5g Aquarium
Lighting: Finnex Planted Plus Cliplight
CO2: None, though Flourish Excel added daily
Fertilizer: APT Complete (all-in-one fertilizer containing all essential nutrients) dosed twice a week
Substrate: Fluval Stratum (nutrient rich aquasoil)
Filtration: none
Maintenance: 20% water change once every 2 weeks and 30 minute trimming session once every 8 weeks. Tank was kept extremely clean with minimal organic waste buildup.


Though these tanks are both lowtech and hightech, there are some common elements between these tanks.
  • All of the tanks use high quality, specialized planted-tank lighting
  • All of the tanks have comprehensive fertilization containing all necessary nutrients
  • All of the tanks have a good substrate (they happen to all be nutrient rich, which aids in plant health)
  • All of the tanks received frequent, consistent maintenance that was scheduled. High tech tanks typically received larger water changes, while the lowtech tanks received smaller water changes, though it was still quite a large volume of water. Emphasis was placed on keeping the tank extremely clean by removing all organic waste and detritus, as well as removing fallen leaves, uneaten food, and decaying plant matter. Even though many of the tanks lacked filtration, they still were kept clean by performing water changes and actively siphoning out organic waste.
  • All of the tanks received proper plant husbandry that involved trimming plants as necessary, maintaining equipment as necessary, maintaining the substrate, etc.

Treating Algae: Creating an Environment for Success
The majority of algae-prevention occurs when the aquarist is actually setting up the tank. More often than not, the products that the aquarist uses to create their planted tank will have a considerable impact on the success they have. To optimize their success for a lowtech tank, an aquarist should try as much as possible to use the following:
  • A great, high quality light. Though it may be tempting to use budget lighting, they are not the best suited for creating an optimal environment for growing plants. Especially considering that the plants already will not have added CO2, it is essential to give them a good source of light. Brands such as Finnex, ONF, Twinstar, Chihiros, ADA, Fluval, or other high quality fixtures are great options. While I will not mention brands to avoid, there are plenty of knockoff options or falsely marketed products on Amazon and eBay that claim to sell “planted tank lights” but the spectrum is typically not well suited for growing plants.
  • An all-in-one comprehensive fertilizer. Fertilizers such as APT Complete by 2Hr Aquarist or the Thrive line by NilocG are all great options.
  • A nutritious substrate. Substrates such as ADA Aquasoil, UNS Controsoil, and Fluval stratum are all good options for substrate. These substrates feed plants and also provide a good medium for the plants to root well in. Mineralized topsoil capped with fine gravel or very coarse sand is also a good, economical option.
    • Even inert substrates are fine to use such as Eco-complete, Seachem flourite, or plain gravel/sand. Root tabs can always be added to the substrate to make it better. It should be known that better results will be achieved with aquasoil, but inert substrates do work too. A fine-sand substrate, however, should be avoided at all costs. The compacted nature of the substrate makes it difficult for plants to thrive in. Sand/gravel grains should be at least 3-4mm in size. Anything smaller than that will be difficult to use.
  • A powerhead or filter. Some sort of device is necessary to encourage good flow throughout the aquarium. Using a circulation pump, wavemaker, HOB, or canister filter are all great options for encouraging good water flow. For aquariums with a fish load, it will be necessary to use an actual filter like an HOB or canister filter to make the environment suitable for livestock.
  • Using established biomedia from another tank. Using established media adds to the biological maturity of the tank in the initial stages, which can help to prevent certain types of early algaes your tank may experience.

To optimize success for a high tech environment, the same recommendations as above apply to go for good lighting, good substrates, and good fertilizers. However, it is also necessary to invest in a quality CO2 system with emphasis on a high quality CO2 regulator. Cheap regulators often have fluctuating CO2 levels, which is terrible for plants. A quality dual stage regulator from companies such as CO2art will provide a safe and reliable product.

And finally, tanks should be planted densely from the start with healthy aquatic plants. The tank should be heavily filled with biomass from Day 1. Using healthy plants are important because they will have a better chance of doing good in your environment if they are already in good health to begin with.

Treating Algae: Techniques and Methods to Use to Avoid Algae
Even if an aquarium is set up correctly, it is up to the aquarist to maintain the aquarium properly to avoid algae. Avoiding algae can be done by doing the following:
  • Performing consistent, weekly water changes with this method, created by Dennis Wong:
  • Remembering to dose your fertilizers consistently and at the recommended dose
  • Remembering to avoid overfeeding your fish to reduce organic waste
  • Dosing mild algaecides like Seachem Excel as a preventative treatment (should not be used with Elodea or Vallisneria species)
  • Keeping plants well maintained and trimmed. The bottoms of the plants should not be rotting away or decaying. The entire plant should be vibrant and healthy. Similarly, plants should not be blocking a ton of light from other plants.
  • Keeping your equipment clean and running properly. Don’t let the flow from filters or pumps get impeded by plant growth. Don’t let the filters get clogged or stay dirty for too long.
  • Keeping your lights on a timer, rather than relying on yourself to do so. Keeping lights on a timer will ensure that the photoperiod is consistent and will be less of a hassle to the aquarist.

Treating Algae: How to Kill Algae that is Already Present
Algae that is already present can be killed and removed by doing the following in order:
  1. Manually remove as much algae as possible. Remember to turn off all pumps and filters while removing algae. If the algae wipes off, a siphon should be started to suck it away. String algae can be removed with a toothbrush. If plants are badly affected by the algae and are close to dying, those plants should also be removed and tossed, or salvaged if possible.
  2. Areas that are difficult to get, or areas that are especially prone to algae should be spot treated. They can be spot treated with this method using some sort of liquid carbon supplement like Seachem Excel or with hydrogen peroxide:
    (Note that plants should not be directly sprayed with these chemicals in open air, as they can easily melt plants upon full contact.)
  3. Large 75-90% water changes should be performed after these sessions.
  4. Algaecides such as API Algaefix or Ultralife Blue-green Stain Remover can also be dosed after manual removal and after the water change to get rid of any other algae that may remain. Note: Beware of which organisms you have that are sensitive to these algaecides and make sure that these chemicals are dosed for the appropriate types of algae at appropriate dosages.
  5. Continue steps 1-3 at a maximum of 2-3x a week for as long as it takes to completely rid your tank of algae. Remember that root issue, being plant health, will need to be fully addressed for algae to truly be eradicated within the tank.

Different Types of Algae and Their Common Solutions:
Not all algae are the same, nor are they created/caused equally. Some are more difficult than others, and they all have their unique causes. This is a list of algae that is commonly encountered (ranked from easiest first to most difficult last):

1) Diatoms:
Diatoms are simply caused by new tanks. Many times, the cure to diatoms is simply to wait it out. Let your filter media become more established and keep fertilizing your plants sufficiently. Keep up with water changes and continue wiping away the diatom algae manually. Chemicals are not needed to treat it. Within a few weeks or days, the diatoms will be gone.

2) Green Water Algae:
If you notice your water starting to get cloudy or developing a green tint, act immediately as this is green water algae. This is a free floating algae that makes the water a dark green if not addressed immediately. It is often caused by an excess of organics due to plants decaying, fresh aquasoil substrate leaching ammonia, and/or overfeeding food. Large water changes, increasing filtration, and adding UV sterilization is the best way to get rid of this algae. Adding UV sterilizers are extremely effective and it is the only way I've quickly gotten rid of this algae without having to perform multiple large water changes over the course of many weeks.

3) Slimy Filamentous Hair Algae:
This is the most primal sort of hair algae. It is caused by excessive ammonia and excessive organic waste in the water. To cure this, manually remove it and perform multiple water changes using the aforementioned water change technique. Algaecides such as API Algaefix are often very effective against it too.

4) Green Dust Algae
This algae forms large biofilms of light green dust over plant leaves and the glass, but it is easy to wipe off. It is typically caused by an excessive amount of organic waste or a high amount of nitrate within the water column. It is common in tanks that follow EI dosing regimen, or in tanks that frequently uproot and trim their plants. Keeping organic waste to a minimum will help to keep this algae at bay, as well as wiping/scraping it off right before water changes.

5) Green Spot Algae:
This algae forms dark green spots that are hard to wipe off. Getting rid of this algae is typically quite easy. It is usually due to a lack of CO2 and phosphates. Simply increase phosphate dosing to a healthy 3-5ppm per dose and if that doesn't work within a few weeks, increase the amount of pressurized CO2 injected as well.

6) Black Beard Algae and Staghorn:
This algae is often notorious for getting rid of, but that is often because treatment is often attempted incorrectly. Most people blast this algae with excel and hydrogen peroxide but it will come back because the root issue hasn't been addressed. This algae is often due to fluctuating/low CO2 levels and an excessive amount of organic waste. Simply fix your CO2 levels (increase it or get a pressurized system) and the algae will turn red within hours and disappear within days. This treatment works for both staghorn and BBA. Additionally, removing organic waste is also a good solution for this type of algae. Aquarists who keep driftwood often notice this algae is attracted to it, likely because of the excessive amount of organic waste that driftwood releases in the water. Spot treatment with Excel or Hydrogen peroxide is quite effective with this algae.

7) Green Hair Algae:
This hair algae isn't coarse, but it isn't exactly soft to the touch either. It looks and feels like hair. This algae is typically difficult to pinpoint exactly what caused it. The best thing to do with this algae is to remove as much as you can manually and then upgrade or clean the filters, and increase the amount of CO2. Keep up with water changes and eventually this algae will go away. API Algaefix is quite effective against this algae.

8) Blue-Green Algae (BGA) AKA Cyanobacteria:
BGA is not technically an algae, but rather a photosynthetic bacteria. It typically appears as a result of chronically low nitrates, and as a result of substrate compaction. It is common in tanks with compacted fine sand and aqua soil that has turned into a fine mush. Changing out the substrate to something more coarse or addressing chronic low amounts of nitrates will help to get rid of it. Additionally, Ultralife Blue-Green Stain Remover is extremely effective at getting rid of this stuff.

9) Cladophora:
This is a very difficult algae to eradicate, but not impossible. It is typically dark green, and grows in tufts or long coarse strings. It is caused by a lack of CO2 and an excessive amount of organic waste, but it tends to be very hardy unlike BBA and staghorn algae. Manual removal is often best and then the increased CO2 and water changes should kill the remaining algae. Algaecides are typically not very effective against it.

Algae Myths
Algae is extremely misunderstood in the aquarium hobby, and many of these myths are fact in different environments. Earlier in the article, planted tanks were distinguished as being unique due to being a closed, plant-dominated system. These unique features make certain types of algae-facts turn out to be myths in these circumstances.

1. “Excess Nutrients” Cause Algae
When people talk about excess nutrients, they typically are referring to nitrates and phosphates. This idea comes from typical pond/lake management which involves limiting the amount of nitrates and phosphates that enter these bodies of water via runoff. But our planted aquariums differ from those systems. Aquarists have dosed extreme levels of fertilizer such as 90ppm of nitrate a week and 15ppm of phosphate a week in high tech environments without algae blooms. Though those sort of nutrient levels are wasteful and unnecessary, it goes to show that nutrients cause algae depending on the system they’re in. Excess nutrients can technically cause algae if one nutrient is dosed in a high enough quantity to inhibit the uptake of other nutrients (such as excess potassium blocking the uptake of calcium).

Often people cut off their fertilizers when experiencing algae to starve it. Unfortunately, this ends up starving the plants more than the algae, which cause the plant to decay and further fuel the algae. As long as fertilizers are dosed at their recommended dose in moderate quantities, then aquarists should not have nutrient-related algae issues.

2. Iron Causes Algae
This is yet another myth that comes from natural environments. In marine ecosystems, iron is typically a limiting nutrient for phytoplankton growth. Adding in iron can cause algae blooms in these environments, but they are not the same system as a planted tank.

Iron does not cause algae within a planted tank. Yet again, nutrients should simply be dosed in moderation at their recommended dose, and algae will not bloom from it.

3. Excel “Cures” Algae
Excel is not a cure to algae. It is simply a diluted algaecide that contains glutaraldehyde. It is not a liquid CO2 supplement, nor is it even close to an alternative to pressurized CO2. It is not mandatory for any aquarium, but can help in lowtech environments or when needed for spot treatment.

4. Sunlight Causes Algae
Sunlight by itself does not cause algae. Light is only an issue when there isn’t enough CO2 or fertilizer to aid in plant growth. CO2 and fertilizer demands from a plant are directly dependent on the amount of light the plant receives. Give plants enough CO2 and light for a source as strong as the sun, and you will not get algae from it.

5. CO2 Injection is Not Natural
Aquatic plants are often observed growing in the wild with no visible CO2 injection. They often grow in clear bodies of water with no visible algae, or along the banks of rivers/streams. It may seem unnatural to inject CO2 into the water, especially when aquatic plants in the wild supposedly grow submerged just fine without it. However, often bodies of freshwater often contain a considerable amount of dissolved CO2 in the 20-30ppm range. This CO2 often comes from organic decay and/or CO2 enriched groundwater. Springfed water systems and rain are especially rich in CO2. Standing water only contains 2-3ppm of dissolved CO2 which makes CO2 injection in the aquarium quite logical to reach the natural levels of 20ppm+.

Key Takeaways
  • Set yourself up for success by using the proper equipment for your planted aquarium
  • Poor plant health = Algae. Place heavy emphasis on plant health by using good plant husbandry techniques
  • Extremely clean conditions help with preventing algae and can be achieved through particular water change methods
  • Having a good, consistent routine will help to prevent algae from forming


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OMGosh, this is insanely informative!! Very well done, you can tell you know what your talking about! Soooo helpful...
What an informative and common sense approach to algae management. I just wish I had read this before starting my tank. Future planted tank projects will be on the right path from Day 1
  • Ghostly
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excellent advise fixed my algie problem
  • Stlshrk
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This is a well written article with lots of information, opinions, and compelling arguments. Thank you for submitting it.
This is an outstanding article. It includes a ton of information and is very comprehensive, very detailed. This gives me hope to fight algae.
Thank you for your feedback, it is greatly appreciated!
  • Tenoch
  • 5.00 star(s)
This is just what I need, plain English and straight forward TO THE POINT! I will increase my pressurized co2 to fight BBA!
Appreciate your review! Thank you!
Excellent post with good advice.
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