Direct vs Indirect Variables to Promote Healthy Prolific, and Algae Free Tanks - The Planted Tank Forum
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post #1 of 2 (permalink) Old 09-09-2016, 07:34 PM Thread Starter
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Direct vs Indirect Variables to Promote Healthy Prolific, and Algae Free Tanks

Direct vs Indirect Control of Variables to Promote a Healthy, Prolific, and Algae Free High Tech Planted Tank

So many people struggle with algae, especially BBA in establish tanks. They treat their tank with CO2 thinking it will eliminate the problem, with mixed results. Others are afraid to dose macro/micro ferts thinking it will make the algae problems worse, only to see their algae problems increase and their plants falter. Others limit light to combat algae problems which works sometimes, but also decreases the ability for the plants to reach their full potential. Others try to decrease algae with huge, frequent, water changes depleting vital resources in the tank. Some resort to dipping the plants with bleach, H2O2, or even using algaecides which is equivalent to the nuclear option in terms of the negative side effects to the fish and plants. All of this is done because of the lack of knowledge regarding the differences between direct and indirect cause and effect. People wrongly think that changes such as the ones listed above directly affect algae growth. The fail to see the system as a whole and realize that algae is a symptom of a bigger problem. Doing one intervention without addressing the entire problem is like treating a bacterial respiratory infection with a breathing treatment alone. Yes, for a time your breathing is better but without treating the core of the problem with antibiotics, your symptoms will soon return. (Im a nurse so sorry for the medical analogy).

After unsuccessfully struggling with algae problems of my own, particularly BBA. I directed my research towards the relationship between overall plant health and the formation of algae on those plants. I have read many articles proposing that algae is caused by lights being too intense and in excess duration. I have heard that algae is caused by light spectrums not utilized by plants. I have also read accounts of high/low concentrations of macro molecules (CO2, Urea, NH3, NO2, NO3, KH2PO4, K2SO4) and micro molecules (Fe, Ca, Mg, Cl, Co, Cu, Na, Zn) causing algae blooms. I have seen it stated many times that you need to have enough healthy plants so that excess nutrients are utilized before the algae can use them. This is the idea behind the theory of plants "out competing" algae for resources. I've read that plants are higher order organisms then algae and therefore, if healthy will have an advantage in using the available resources.

While at first glance these ideas about light, chemicals, competition, higher order seem like they could have credibility. The problem with many of these articles is the disconnect between true cause and effect. In complex system such as a planted tank, it is highly unlikely that simply altering one or two factors of the above variables will prevent the majority of algae. Sure plants benefit from CO2, removing NH3, and having adequate light. The problem comes when people believe that excesses/deficiencies of the above variables directly causes algae to grow. This is where the disconnect between direct and indirect cause and effect come into play.

What is the difference between direct vs indirect cause and effect? A direct line of cause and effect states that "X" causes "Y". An example of this would be, adding CO2 prevents algae growth. An indirect line of cause and effect states that "A" causes changes in "B", "B" then alters "C" which is ultimately responsible to "D". An example of this would be, adding CO2 increases its ability respond in an effective and healthy way to light stimuli, thereby increasing the overall health of the plant, which allows it to combat algae growth more efficiently. The fact that big algae blooms are more prevalent in high tech tanks then they are in low tech tanks is interesting. High tech tanks involve adding variables such as high light, CO2, and added ferts. Based on these variables, I could see why some people believe that high/low levels of these variables directly result algae growth. The thing to remember is that, first and foremost, healthy plants can very effectively resist algae growth. Secondly, algae is primarily and directly caused by poor overall plant health. All other potential issues are almost a none factor if your plants are in poor health.

What is algae and why does it grow? First, algae is not a plant. Although there are many different types of algae they are basically single celled (or simple multicelled) photosynthesizing organisms. They utilize the same chemicals (give or take) that plants do. The can grow very quickly and form spores that aid in their reproduction. Because the form spores they are usually always present even if they are not actively growing. Thats why algae can seem like it came out of nowhere. Next, where do you see the majority of the algae in your tank growing? Does it grow on new plant growth that is green (or red) and healthy, or does it grow on older growth that is damaged or in some way unhealthy? Unless algae has completely taken over the tank, you generally only see it on weaker old growth.

After acknowledging that algae formation directly relates to the health of the plant as a whole I was able to better understand the variables that go into preventing algae. It helps to learn that healthy plants have certain defense mechanisms that prevent algae and when the plant is unhealthy, the defense mechanisms fail, resulting algae growth. Think about it, all organisms have evolved overtime to have the best chance to survive and then reproduce. What is the most basic component of plant growth and therefore survival and reproduction? The answer is light, without it nothing is possible. So in terms of survival, can a plant absorb light for photosynthesis if it covered in algae, Absolutely not! Due to this survival need, plants have developed certain protections from algae. Some have stated that plants engage in a type of chemical warfare called allelopathy. Though it does happen in nature, there is no conclusive data regarding the plants in our aquarium.

I honestly don't think it needs to be as complex as chemical warfare. Plants have passive immune systems meaning that while they do not have circulating immune cells, they do have inherent defenses in their cells, especially the outer areas exposed to the environment. This type of passive immunity can help prevent algae growth. If a plant is deficient in resources, it will use those limited resources on new growth at the expense of old growth. This is why algae primarily grows on weak or damaged, older growth. So knowing this, how do plants become weak and damaged, particularly in older areas? This can be caused directly by physical destruction such as a fish destroying part of the plant causing the plant to expend more energy and resources to repair the damage. When physical damage is eliminated from the equation, the cause for weaknesses in old, and to a lesser extent, new growth comes from deficiencies in resources such as light, CO2, and macro/micro nutrients.

Before we can tackle to algae problems in our tank, we must understand two vital concepts. First, understanding the difference between direct and indirect cause and effect (described above). Second, we must understand what a LIMITING AGENT is and how it affects the system as a whole. A LIMITING AGENT is any factor, that when deficient, effects the plants health negatively and consequently decreases its ability to combat algae. Examples of these limiting agents are light, CO2, ferts, and circulation in the tank.

Below is a list of reasons people claim algae grows in a tank. While there may be some truth in the reasons below, it is important to note that many are incomplete and lack in insight needed to treat the core problem instead of covering up a symptom.

1) Many people believe that high levels of light, in long durations, directly cause algae to grow. So is this true? At high levels, does light directly cause algae? Although long and intense photoperiods can cause problems, I argue its only when the other factors such as ferts and CO2 are not provided for. I argue that high light does not cause algae growth directly even in longer durations, assuming the only limiting agent is the light itself, and provided your not running your lights 20 hours a day. Remember, the light is the gas pedal, if the plant is exposed to high light its metabolic demands will increase. Knowing that high light increases the metabolic demands of the plant, what do you think would happen if the plant doesn't have the fuel to sustain its metabolic needs? Remember, plants prioritize new growth over the preservation of old growth. This desire to continue its growth in presence of high light is undeniable, even if that growth is weak and at the expense of older parts of the plant. If there is insufficient levels of resources such as CO2 and ferts (limiting agents), then the plant will become compromised in one way or another as it becomes unable to support the increase in metabolic demands. This compromise in health, especially in existing growth or weak new growth, decreases the plants natural defenses. These inadequate defenses are what provide a foot hold for algae. So even under high light situations, if the plants has all of its needed resources, algae shouldn't be an issue. So while light level directly affects the plants metabolic rate, it does not directly cause algae to grow on those plants.
2) What about CO2? It is commonly held that CO2 prevents algae growth. Granted CO2 is a staple in the high tech tank, it does wonders for plants and is a key component in cellular respiration within the plant. But does this directly prevent algae from growing? The main reason that CO2 is touted as a cure all for algae is because in most tanks it is the LIMITING AGENT in the system. Our tanks usually have plenty of light and nutrients come from fish food, decaying plant matter, and fish waste. What makes CO2 the LIMITING AGENT is the fact that max diffusion of atmospheric CO2 results in a water concentration of about 7ppm of CO2. This okay in low tech tanks where the plants do not need as much CO2 to support their metabolism, but in high light planted tanks you need upwards of 30ppm. So sure, you add CO2 and maybe you saw less algae. This wasn't because the CO2 directly affected the algae. It helped because you removed CO2 as the LIMITING AGENT, which made your plants healthier and more capable of fighting off algae.
3) Many people state that high levels of macro/micro molecules, specifically phosphorous, nitrate, and calcium cause algae to grow. Is this idea sound? It is important to realize that if there are detectable levels of ferts in the water column, even at low levels, then there are resources for algae to exploit. Even if the plants are operating at their max ability to absorb ferts, and you have a heavily planted tank, there are still resources for the algae when nutrients are detectable even at very low levels. For some reason people have this idea that the plants and algae are physically wrestling for resources. If a you have a plant and some algae say an inch apart, and a molecule of NO3 float by, the plant wont snatch it from the algae. Which ever organism the NO3 passes first is the one who gets to use it. So regarding liberal nutrient dosing, contemplate this example. You set up your high tech tank with everything you read about. You have nutrient rich substrate, 4 high output T5s, CO2 at 30ppm, timers, circulation fans, the works. Your tank is cycled and everything is going well. Then 4 months pass and you notice your plants not pearling as much, the old foliage is looking shabby, and the new growth looks okay but very slow to develop. You check your water chemistry and the nitrates are high, you do an extra water change and things don't improve or even get worse. You read somewhere that PO4, NO3, and Ca can cause algae so you are afraid to dose them and make the problems worse, you try more CO2 which doesn't help. You decrease your light levels to 6 hours a day, no benefit is seen and the plants are starting to die while the algae is multiplying. What is going on? You did everything right; water changes, upped the gas, decreased the light, tried to keep those awful algae causing macro/micros out of your tank and things kept deteriorating. The root of the problem was after you tank used up the nutrients from the enriched substrate, your micro and macro resources became a LIMITING AGENT , this caused the health of your plants to suffer, lowering their ability to defend themselves from the algae. Your large water changes further depleted your supply of micro/macros and compounded the problem. You wrongly assumed, due to poor information on the forum you subscribe to, that excess nutrients have a direct influence in growing algae. You do more research and accept that excess nutrient levels do not potentiate algae growth. You also realize that when your micro/macros become a LIMITING AGENT, it directly causes deficits with your plants and then indirectly potentiates algae growth. After all this, you remove all the algae riddled plants, discover EI dosing (dosing in excess) for KNO3, KH2PO4, and trace elements, and EI dose after every water change even when your NO3 readings are 10-20. You see your remaining plants bounce back and look better than ever, all due to eliminating nutrients as your LIMITING AGENT. This is why I do not subscribe to the idea that fert levels directly cause algae growth. The one caveat to this would be in cases of high ammonia which some algae can utilize better then plants as is usually the case with green water algae. So besides ammonia, the key point to take away is this. Excess nutrients do not have a direct effect on algae growth but when those nutrients become a LIMITING AGENT they directly harm plant growth and indirectly CAUSE ALGAE GROWTH.
4) Some say adding a powerhead with help combat algae. Adding more circulation will undoubtably help your tank, but is it directly doing anything to the algae? By adding more flow, you are helping with the distribution of the resources and preventing any local area of the tank (dead spots) from suffering the ill effects of LIMITING AGENTS.

So many times we read articles about the need to keep everything in balance. While it is true that if everything is in perfect balance, you should not have issues with algae. The problem with keeping such strict parameters comes when we fail to realize that you tank is not a static system. The requirements for each of the variables (light, CO2, ferts) is constantly changing. Eventually, by using the "keep everything balanced" model, your CO2 or ferts will become a LIMITING AGENT. This is guaranteed to happen at some point, due to the vast complexity of the system as a whole.

So instead of trying to keep an unrealistic, perfect balance of variables, I aim to provide and excess amount of any potential LIMITING AGENT. When this is accomplished, the excess resources can provide "wiggle room" for any change in the plants metabolism, and therefore prevent deficits that can promote algae. Of course I don't what to take my excesses to extremes and cause toxicities. That being said, there is little ill effect that can come from having a little cushion in your resource levels for increased plant demand.

When all the other variables are controlled for the only remaining LIMITING AGENT becomes the light level. This should be the ultimate goal in any planted tank. The light level is one of the easiest things to control. If you want to lower the light intensity, increase the distance between the light and your tank. If you want to apply more or less light duration, simply adjust your timer. You can now safely do this because you know everything else is controlled for. You can now directly effect the metabolic demands of your plants, which directly effects their need for resources. Your dosing in excess directly supports your plants health, which indirectly prevents algae growth. You now have NEARLY complete control over the outcome of your tank. I say nearly because is always something that can go wrong such a power outage while your on vacation, CO2 running out without your knowledge, mechanical failures, ect.

So in conclusion if one is going to have healthy, lush, and vibrate plants that are free from algae, we must member a few key facts.

1) Algae exploits vulnerabilities in plants, that means algae growth (in large amounts) is directly related overall health of your plants
2) Healthy plants have defense mechanisms that can very effectively combat algae from growing on them WHEN THEY ARE HEALTHY.
3) The most direct way of fighting algae is to provide all LIMITING AGENTS in excess to directly influence the proliferation of HEALTHY PLANTS
4) The only direct way to eliminate algae is to nuke it (bleach, H2O2, algaecide) which is not advised. One can only indirectly prevent algae growth through good management of CO2, micro/macros, and light.
5) Simply adding or subtracting one type of resource without providing for the other plant needs is unlikely to prevent the growth of algae.
6) Always aim to make the light the SOLE LIMITING AGENT, this will allow you to directly control the metabolic demands of the plants, thereby directly controlling their need for resources, and indirectly eliminating algae
7) A moderate amount of excess resources will only benefit the tank, not promote algae.
8) Question everything you read, even what I have described to you. This will only benefit you, and the hobby as a whole.

Long read I know, but thanks for sticking it out. Let me know what you think!

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post #2 of 2 (permalink) Old 09-11-2016, 02:54 AM
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I think you have written a defense of Tom Barr's Estimative Index method for fertilizing plants. You repeated most, if not all, of his reasoning when he promoted this EI method. Yes, you used different words, sentences, etc. but in all but minor details you just paraphrased the EI method explanation. Sorry.

One problem with long explanations/recommendations is that you tend to lose your readers before you reach your conclusion. So, I suggest editing this to tighten it up, and crediting Tom Barr for originating this reasoning.

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