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Algae Control: Filamentous, string, hair algae

Updated: Dec 21, 2022




DEFINE - What is Filamentous algae?

Filamentous algae, also know as string or hair algae look a lot like really fine, long hair. It can grow in little bunches or become long in a high flow area of your tank.

General causes:

  • High phosphates

  • Low flow

  • Stressed plants, or old growth coupled with the above






REMOVAL - How to remove Filamentous algae

The methods we are about to mention will tt help prevent filamentous algae from coming back. We'll address that shortly. But here are a few ways to remove it from the tank.

  1. Hydrogen peroxide - Remove the affect plant or hardscape from the tank. Fill a squirt bottle with hydrogen peroxide and spay the affected area and let it sit for a few minutes. We suggest to remove it from the tank so that you can rinse it well with dechlorinated water before putting it back into the aquarium. You can spray the affected areas inside the tank, but know that using too much hydrogen peroxide can kill livestock and more sensitive animals like invertebrates. This is why we suggest remove the affects plants or hardscape.

  2. Bleach dip - There is very little that can survive a cleach dip. Mix 1 part bleach to 20 parts of luke warm water. Sensitive plants, like crypts, dip fro no longer than 90 seconds. Heartier plants like anubias can be dipped for 150 seconds. Do no dip mosses and rinse REALLY well with dechlorinated water after the dip session.

  3. Toothbrush - This may sound funny, but you can take a toothbrush, to the effect area. Hook a small amount of it on the bristles of the toothbrush and twist like you are eating spaghettis. The algae will get caught up in the toothbrush and wrap around the head.

Note. If you can not use options 1 and 2, because its infested a moss. You may need to trim the affected areas until its gone, or remove the moss all together. Once you've taken all the preventative measures in the next topic, it may stop coming back.


Solutions - How to keep Filamentous algae from coming back

I am going to say this in every algae article... we need to make changes to how we've designed our aquarium otherwise the algae will just keep coming back. The definition of crazy is: doing the same thing over and over, yet expecting different results. Do not rely on fish, algae eaters, snails, shrimp etc., to fix the design flaw that we've introduced into our tanks.


Solution 1: The most common reason we see hair algae is due to high phosphates. Adjusting our phosphate levels can fix the issue. Check your phosphate levels and make sure they are in a 1:10 ratio with nitrates. Meaning, 1ppm of phosphate to 10ppms of nitrates. This is referred to as the Redfield ratio and is the ratio in which plants uptake nutrients. When nutrients falls out of the redfield ratio, we can see algaes like hair algae. We suggest using API's phosphate test kit to check where your phosphates are at. Just note that once you reduce your phosphates that it could take 2-3 weeks after removal for the alage to subside. So be patient and keep phosphate levels under control.


Here are some sources of phosphates to avoid:

  1. Tap water - Excess phospates can come from your tap water, so make sure we are not introducing more phosphates with water changes. If phosphates are high in your tap water, the best way to remove them is by using an RODI filter, which we talk about in this article, and in this video.

  2. Cheap fish food - Extra phosphates can be introduced from cheap, flake or dried fish foods. Phosphates are used as a preservative. If you have a lot of fish, and are feeding them a lot, you could be introducing phosphates into the tank manually. Try reducing your feeding, or switching to more nutrient dense foods like brine shrimp, blood worms, or mixed frozen packs. You'll notice your fish will appreciate the higher quality food as well.

  3. Seachem Buffers - For those of you heavily relying on Seachem's buffers to help fix your water's chemistry, this is a great reason to stop. Most Seachem buffers heavily rely on phosphates to help deliver their chemicals. These dissolve into the water column and can push us outside the redfield ratio. The more of a buffering agent you use, the higher the chances are you'll run into hair agales. This is another reason why its not a great idea to rely on buffers to help fix out water chemistry. Learn how to properly adjust your GH/KH/PH in this video. Stop relying on easy fixes.

Solution 2: If and only if phosphates have been adjusted, then you can move to circulation. Remember that circulation is very different from your filters turn over. Make sure to position the outlet of your canister in a manner than helps increase circulation around the tank. And if you have a larger tank with dead spots, a powerhead (one speed) or wavemaker (variable and programable speed) can help.


Solution 3: Focus on overall plant health. We are going to say this whenever addressing algae because happy plants fend off algae. When plants are happy they produce allelochemicals which are a defense mechanism for agale. But they can only produce this chemicals defense mechanism when thriving. As they say, an ounce or prevention is worth a pound of cure. If you are not currently running the ASG method, we would highly encourage you to do so. In the ASG method we teach you to:

  • Lighting: Have your light on a timer for 6-8 hours and ensure its outputting 80 PAR for non CO2 injected tanks, and 120 PAR for CO2 injected tanks. Learn all about PAR in this video. Reducing the PAR for a week or two can help reduce the excitement of algae.

  • CO2: Ensure your PH drops one full point before your lights come on, and stays there for the duration of the photo period. You can check your PH with an API PH test kit. Learn all about the PH drop method in this video.

  • Nutrients: Combined an aquasoil with a holistic fertilization method, like Thrive all in one, or the EI Method. Since aquasoils have a high CEC, they will absorb the nutrients from the water column and feed it to root feeding plants. This is the most efficient way of providing nutrients for both root feeders AND water column plants like mosses and floaters. Learn all about providing nutrients in this video.

  • Water chemistry: Main a GH/KH of 4, unless livestock dictate otherwise. Example, neocaridina shrimp like harder waters as in a GH of 8-12, and a KH of 2-6. Let your livestock dictate the GH/KH. Your PH will be what it is. Learn how to properly adjust your GH/KH/PH in this video

  • Filtration: Ensure your filter is able to turnover your entire water volume 10x an hour. Also ensure your have dedicated mechanical and biological filtration, and they are separate from eachother. Sponge filters just don't cut it. Learn how to properly set up your filtration in this video.

  • Husbandry: Once a week we should be processing a 50% water change. 75% water change when dealing with an algae issue until we can get things back under control. Remove 10% of the water to avoid splashing when cleaning surfaces. At this time you can scrape the glass/hardscape down THEN remove the rest of the water. This remove the algae we just scraped as we don't want it settling back into the tank if we can avoid it. Also make sure to kick up and remove any detritus from the corners or hard to reach places in our tank. Rotting organic matter in the tank can just cause unnecessary ammonia spikes which can lead to other alages.

If you are new to the ASG method, check out our Part 1 series on YouTube here! We cover all the topics above in more detail.



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