Psa: Algae Myths In The Planted Aquarium (algae Management Part 2)

Discussion in 'Aquarium Plants' started by Vishaquatics (Koiman), May 23, 2019.

  1. Vishaquatics (Koiman) Well Known Member Member

    Hi FishLore,

    Here's part two of algae management in the planted aquarium. This thread is mainly going to cover myths about algae that are just simply wrong and are due to a lack of experience as well just plain old misinformation.

    Myth 1: "Excess Nutrients" Cause Algae

    This is by far the biggest myth when it comes to algae management in the aquarium. When people talk about "excess nutrients", they are usually referring to nitrates and phosphates. The amount of times I've seen this term, "excess nutrients", is absolutely mind blowing.

    Excess nutrients do NOT cause algae of any form including hair algae, BBA, green spot algae, and green water algae. There is only one nutrient/type of nutrient that causes algae and that is ammonia. Most aquarium fertilizers do not contain ammonia, but ammonia is produced by organic decay AKA uneaten fish food, fish waste, dying plant matter, detritus, dead fish, etc.

    Nitrates and phosphates do NOT cause algae. In my tanks that are outdoors in full, direct sunlight, I dump in phosphates and nitrates plentifully. I'm talking around 90ppm nitrate per week (15ppm dosed per day) and 15ppm phosphate per week (5ppm dosed 3x a week). According to the idea that "excess" nitrates and phosphates cause algae, I should be having an algae disaster right now. But I'm not. The theory that nitrates and phosphates cause algae is just simply outdated when applied to freshwater algae. Yes, adult algae consumes nitrate and phosphates but they don't last long in their life cycle. The spores need ammonia to manifest into adults. People neglect to acknowledge that agricultural runoff (often the most common source of nitrate/phosphate pollution), often contains lots of inorganic ammonium fertilizer and manure (organic waste) which is plenty of ammonia to cause an algae bloom.

    Myth 2: Fertilizers Cause Algae

    Going off of the previous point, fertilizers do not cause algae. It is common for someone experiencing algae to cut off their fertilizers in an attempt to "starve" the algae. Starving the algae is absolutely ridiculous. Your plants will starve far sooner than the algae will. In fact, the algae will feed off of the starving plants as they inevitably decay and release ammonia. Preventing algae equates to dosing complete macro and micro fertilizers so that your plants are healthy and will not decay.

    Myth 3: Iron Causes Algae

    This was definitely a rarer myth, but comes up enough for me to feel the need to mention it. The logic I've seen to justify this claim goes something like: "Iron is very important for chlorophyll production so therefore it is also responsible for causing algae". There have been some cases documented on some planted tank forums where adding lots of algae apparently "causes" the algae. When the iron is lowered or removed, the algae subsequently goes away. One thing to acknowledge about these cases is that these tanks are often new. When the person stops iron dosing, the tank becomes algae free within a few weeks. This could be merely coincidental, as algae subsides as the plants adapt to the tank's specific conditions and the CO2 injection stabilizes and reaches its ideal amount for that particular tank. In newer tanks, a few weeks is a very long time as many changes and boom/bust cycles of algae tend to manifest within a short period of time. I've dosed tons and tons of iron without any algae growth. Anywhere from 0.3ppm to 4ppm per day. 4ppm is very extreme and really is just a waste of iron. I aim for 0.5ppm 3x a week.

    Myth 4: Excel "Cures" Algae

    This is another myth that is commonly parroted. Excel is simply a diluted solution of a biocide that is often marketed as "liquid" CO2. Excel is not liquid CO2 and does not provide a noticeable amount of carbon for aquarium plants. It can be used to treat algae, but it is not a cure. The root cause of algae is often CO2 deficiencies and ammonia in the water. Excel can be used to kill stubborn adult algae, but it is by no means a cure to the actual problem in the aquarium since it is not addressing the root cause of the algae in the first place.

    Myth 5: Sunlight Causes Algae
    Many people are often afraid to let any sunlight hit their aquariums since it "causes" algae. Light is only an issue in the aquarium when there are not enough CO2 and fertilizers to aid the plant growth. In a planted tank, think of light as the independent variable in a science experiment. This variable can be manipulated to be low light (half a watt of light per gallon) or extremely high light (direct sunlight like my outdoor tanks receive). CO2 and fertilizer demand are the dependent variables. As the light increases, CO2 and fertilizer demand increases as well. If you have a light as powerful as the sun hitting your tank and you don't have CO2 or fertilizers, then yes, you will get algae. However, if you have sufficient CO2 and fertilizers, let your tank bask in sunlight. Your plants will love it and display levels of coloration and texture that will reinvent the way you view your plants. CO2 levels and fertilizer levels can be adjusted to even handle the highest level of light.

    Please let me know if you have any questions or more myths as well that you'd like to share. Thanks for reading!

    If you want to evidence of algae free tanks, please take a look at the links in my signature as well as my instagram @vishaquatics.

  2. Nick72 Valued Member Member

    Thank you @Vishaquatics (Koiman) for another insightful writeup regarding algae growth in the modern aquarium.

    So the three important variables are light, C02 and fertilisers (both macro and micro).

    For clarity, should a well established planted tank be running in balance of the above three variables for some period of time. What would be the affect of suddenly doubling up on the fertiliser dosage?

    Would you expect this to have no affect other than wasting fertilisers?

  3. candiedragon Well Known Member Member

    What about other liquid co2 boosters? Are they all the same, like API CO2 Booster, Easy Carbon, NilocG Carbon, or Dustin's Fish Tank CO2 Booster? Also, do you have any thoughts about NilocG's newer product ThriveC which apparently has a non glute-based carbon source?

  4. -Mak- Fishlore VIP Member

    Another great write up! Unfortunately I've been on here for 2 years now and these myths will not go away. I wrote a guide on macros+micros when I was new here, it's stickied in fertilizers but I think people tend to ignore the stickies sometimes haha. Anyways thanks for spreading this good info!

    All the same. Dilute glutaraldehyde, though Seachem calls theirs polycycloglutaracetal.
    Colin hasn't disclosed what the carbon source in ThriveC is, probably to protect his business :(
  5. toeknee Well Known Member Member

    One thing I've always been a bit confused on. For low tech tanks running no CO2 how do we address algae caused by CO2 deficiencies? Especially when I have no interest in adding a CO2 system
  6. Vishaquatics (Koiman) Well Known Member Member

    There is no solution here. Lowtech tanks are difficult to get algae free. There are a few things though that you can try to prevent it in the first place.

    1) Plant extremely dense in the beginning. I’m talking very very very dense. It should be packed with plants, preferably submersed grown. The plants need to be fast growers

    2) Use a soil substrate capped with sand. The Soil layer should be thick and as it decays, it releases CO2. This has its drawback though because it also releases ammonia as it decays which is also bad.

    3) Use a good light, but a low light. I constantly see people trying to grow plants with a subpar light for their tank. Use 6500K lights and make sure that if you’re using CFLs or grow lights, there’s less than 1W per gallon.

    Once you get algae in a Lowtech tank, you can use excel or hydrogen peroxide to nuke it but there is no real solution to a lack of CO2. Most aquatic plants are only adapted to temporary submerging. In the wild, Most of them grow above the water line with access to atmospheric levels of CO2 so they are adapted to growth with high levels of CO2.

    Most of them are glut based, but I’m not familiar with Dustin’s CO2 Booster or NilocG. I’d be more inclined to recommend the one of from NilocG since it’s not glut based but that could go both ways with his formula being more toxic than glut

    Yes, the three most important variables are CO2, light, and fertilizers.

    Is there any reason why you’d want to double the fertilizer? For tanks with CO2, I always recommend EI dosing (estimative index). There’s a lot of info on this on

    If you double the fertilizers and you are already fertilizing sufficiently (no deficiencies present), then nothing will happen besides the waste of ferts. If the ferts are continually doubled without water changes and the levels are extreme, then you may experience nutrient blocking. For example, high levels of potassium block calcium uptake. So I’d be a bit careful doubling up if you’re already dosing plenty. gives normal ranges for nutrients in a tank.
  7. happyscrub Valued Member Member

    I can't find any source to back up the claim that algae needs ammonia. That sounded like nonsense especially since algae is one of the oldest organics on the planet and had ample time to evolve to use just about all forms of nitrogen in the 1000s of species we have.
    Last edited by a moderator: May 24, 2019
  8. Vishaquatics (Koiman) Well Known Member Member

    Check out some studies conducted by botanist and professional aquarist Dr. Tom Barr on the Barr report. Also check out algae management videos from greenaqua on YouTube, a famous aquascaping channel. Even check out Dennis Wong’s algae management as well from .All my algae management techniques are based on Tom Barr’s methods and they work beautifully.

    I’ve also done some experiments myself to verify. In a balanced planted tank when you add around 3-4ppm ammonia, you almost always will get an algae bloom. Particularly green water algae and hair algae. I add way more nitrate than that and get no algae bloom.

    Here’s another source:
  9. happyscrub Valued Member Member

    You do realize the 2nd paragraph in your source says, "Any form of nitrogen spurs algae growth "?

    I'm not saying that you don't know how to control algae, but your scientific reasoning is off.
  10. Vishaquatics (Koiman) Well Known Member Member

    No I definitely understand your argument here and it is a fair one. But adult algae is the one that uses nitrates. The spore algae does not. The adult algae has a short life span. Once the spores cannot become adults, there will be no visible algae. The algae spores need ammonia to become adults. So yes, any nitrogen supports algae growth, but sooner or later the adult algae will die. Once they die, a lack of ammonia and abundance of CO2 and other fertilizers will prevent the spores from becoming adults.
  11. happyscrub Valued Member Member

    Listen. Algae, let alone the spores, are microscopic. The only way you can prove algae needs ammonia as a scientific fact is in a laboratory setting. I'm pretty sure when you was doing your experiments of dumping fertz into tanks or ponds outside, you were not putting water slides under microscopes to identify algae, spores, and using chemical test to verify 0.00 ammonia (which would be almost impossible outside a lab). I'm pretty sure you will win a prize, get renown, and have your article published in the scientific community if you can prove it
  12. Vishaquatics (Koiman) Well Known Member Member

    Yep, you’re right. But what I did “dumping fertz” into my pond outside seems to fit nicely with my current theory. Also all of my other experience as well as many renowned planted tank aquarists point to this theory being true. Maybe in the future I’ll have access to a laboratory to prove this.

    The methods I’ve listed and my own experience are legitimate and I’ve helped countless customers and friends rid their tanks of algae. Sure, my scientific reasoning could be incorrect since I don’t have laboratory conditions to completely verify the working theory. However, all of my experience thus far and the experience of countless other experts in this area agree with this current theory.

    If you think that nitrates cause algae, then why don’t my tanks have tons of algae? 90ppm of nitrate per week not even accounting nitrates from the bioload is quite extreme. Why don’t my tanks have an immense algae bloom right now?
  13. happyscrub Valued Member Member

    I don't know why your tanks are what they are. I don't even know anything about your tanks to begin with. But me not knowing something doesn't prove something else to be true.

    That's like saying, " if aliens do not exists, then why so many people say they saw them?" Me being unable to know what those people really saw doesn't prove alien exists or not.
  14. Vishaquatics (Koiman) Well Known Member Member

    Not exactly sure that analogy would work. Unlike aliens, my tanks are right here right now for you to analyze. Here are some stats:

    Size: 100 gallons and 220 gallons

    Lighting: 8-10 hours of direct sunlight with no filter

    CO2- Pressurized and diffused

    Ferts: EI Dosing with nitrates dosed everyday

    Filtration- twice the tank capacity. 3 stage canister filters from Penn Plaxx (Cascades)

    If you don’t know what causes algae, then how can you say that my own theory is wrong? If you claim that nitrates cause algae, then my tanks and countless other aquariums serve to prove that theory wrong.
  15. -Mak- Fishlore VIP Member


    Nitrate will definitely help "adult form" algae along once they have already established, but with proper management there shouldn't be much adult form algae in the first place.

    The main takeaway is that there are many professionals and advanced hobbyists dosing upwards of 40 ppm nitrate regularly without a speck of visible algae. Good maintenance skills are also often overlooked, organic buildup (and the resulting ammonia) will cause algae too.
  16. happyscrub Valued Member Member

    Thank link goes to even more bogus claims. Not only did it say algae spores needs ammonia, but adds that adult algae need nitrate. That's double the bogus claims that many sources say is wrong and I can't find one scientific source to say otherwise.
  17. SeanyBaggs123 Well Known Member Member

    Haven't provided any sources to support your claim either to be fair...
  18. happyscrub Valued Member Member

    Here's one to discredit the 2nd thought from the website stating adult algae needs nitrates (I saw this while looking up spores)

    Now on the topic about spores, if it's a bogus claim I wouldn't be able to find anything on it. That's like me trying to find proof that rabbits don't hunt and kill lions. There would be no reference to rabbits and lions practically anywhere.
  19. -Mak- Fishlore VIP Member

    I'm so confused. Your own article outlines exactly how algae uses nitrates. And you're saying it's bogus that adult algae need nitrate? Please correct me if I'm misunderstanding.

    "In photosynthetic eukaryotes, nitrate assimilation is performed by two transport and two reduction steps: First, nitrate is transported into the cell, then a cytosolic Nitrate Reductase (NR) catalyzes nitrate reduction to nitrite, which subsequently is transported into the chloroplast, where the enzyme Nitrite Reductase (NiR) catalyzes its reduction to ammonium"
  20. happyscrub Valued Member Member

    I was bored and spent 2 hours off an on looking up the subject and I can't find one thing about the subject. The only thing I saw close to it was that when ammonia is high, some algae will chose to reproduce sexually over asexually. Also roads keep leading to this book " " That has a pay wall

    Abstract suggest that this algae spores needs phosphates and do better in high ammonium.

    "Enteromorpha spores seem to be particularly sensitive to PO4–P limitation and to NH4–N  , which suggests a higher sensitivity to the variation of external nutrient concentrations than adult macroalgae. The present results contribute to increase the understanding about the factors that control macroalgal growth at its early phases of development. In particular, the results suggest that the growth of spores from opportunistic green macroalgae is strongly salinity-dependent. Consequently, in highly   systems such as most shallow  , salinity variations may play a   role in the yearly abundances of green macroalgae, since it controls macroalgal growth from the spores to the adults."