Anonymous_One
Active Member
- Sep 1, 2024
- 112
- 177
1) I agree with @Art that when it comes to actual preferences of aquarium plants, we still know too damn little to draw any definitive conclusions. It certainly has to do with a multitude of factors that may play a role in it (e.g., nutrient uptake and mechanisms of their management, their optimal internal and external concentrations and their synergistic or antagonistic relationships with each other, water physico-chemical parameters, sediment properties and composition, light intensity, microbial activity, redox, etc.). Basically, each of us just has a recipe that has worked more or less well for him [in his particular conditions]. And most of our discussions revolve around promoting (sharing) these specific (local) recipes of ours in the wider aquarium community, where we very often find that what works for us doesn't work for [some] others for some reason. But few people think about why. Few look for deeper principles (laws). At least that's how it appears to me.
2) There is a similar discord [from my perspective] in the aquarium community regarding the correlation between higher nutrient concentrations and algae. While the scientific community acknowledges this link, the aquarium community has taken the view that there is no causal relationship between nutrients and algae. However, from my point of view, this is again comparing apples with oranges. This inconsistency seems to me to be due to overlooking other factors that play a role in this (especially the preferences of different algae species with respect to water parameters, light, temperature, pH, redox and optimum nutrient concentration). For example, it has been confirmed to me several times in my experiments that green haze, for example, is much more likely to occur [under certain conditions] in acidic water, whereas bacterial haze or green filamentous algae is more likely to occur in water with neutral pH. Just change the pH and you can be done with the problem. But I mention this only as an example of how little we know about the actual causes of some things/problems, and how often we cling to an opinion without considering other possibilities.
3) I also agree with @Art that nutrient availability and [related] environmental stability certainly plays an important role. If only for the reason that plants adapt to any changes in the external environment (e.g. by activating or deactivating various mechanisms that result in various metabolic changes, etc.), and some of those adaptations are quite exhausting for them. For example, if plants have a steadily higher CO2 concentration (say 10 ppm) available to them, then carbon uptake is so energy-inefficient that it saves them a lot of energy that they can spend on things other than carbon acquisition. However, if they don't have enough CO2 available and are forced to resort to carbon extraction from HCO3 (if they can do that at all), then they supposedly use so much energy to do that that they [or some of them] then need illumination of at least 80 µmol PAR to maintain a positive energy balance. And there are certainly many such examples where one is related to the other.
4) Regarding the optimal ratio of nutrients and their absolute (specific) concentration, I think there is again a considerable discord here, where every aquarist has a different opinion. One of the few things we can hopefully all agree on is that plants take up different nutrients in different amounts, with the greatest demand [ignoring water = hydrogen and oxygen] being for carbon and then nitrogen. The other nutrients they need [compared to these two nutrients] in much smaller quantities. And while the specific optimal ratio of most nutrients is fairly well known for terrestrial agricultural crops, not many people have investigated this for aquatic plants. In general, the optimal Ca:Mg ratio tends to be in the range of 2-6:1. However, many things may be different for aquatic plants because aquatic plants are surrounded by nutrient solution, so most nutrients are "passively pushed" into them and they do not have as good a means of regulating their uptake as terrestrial plants, where most nutrients are bound in the soil and the plants have to "actively extract" them when needed. This suggests to me that the optimum nutrient ratio may play a much greater role in aquatic plants than in terrestrial ones, since here the internal balance of charges can be upset much more easily by an inappropriate nutrient solution. However, it should certainly be borne in mind that many plants may be better adapted to these problems than others. But here again, I think that many (perhaps most) aquarists often focus on nutrient ratios without considering other factors that may play a role. For example, think about how many aquarists include such a trivial parameter as pH or redox (water/soil) in their tank journals. Virtually none. Yet I consider both of these parameters to be crucial, as they have a cascading effect on a whole host of other things (from nutrient availability to microbial composition). Another thing that is often overlooked when considering optimal nutrient ratios is the fact that most essential nutrients (including calcium, magnesium and potassium) are present in some quantity in organic sediments. And while the prevailing opinion in the scientific community is that most aquatic plants prefer to take up these nutrients from the water column, this may be far from being true for all aquarium plants. In other words, whatever concentrations of Ca:Mg:K we have in the water, these concentrations may be in completely different ratios and concentrations in the sediment, and if [at least some] plants can obtain these nutrients in adequate amounts from the sediment as well, then this may distort the overall picture, and knowing their exact ratios and concentrations in the water may be of little use ... because we are again overlooking another factor (= sediment).
My point here is to show that, while I welcome discussion of these matters, I think (and hopefully have managed to present some meaningful arguments for it) that unless we learn to evaluate the phenomena that take place in our aquaria in the broader context of all the relevant factors that may have a major influence on them, we will hardly reach any meaningful (generally valid) conclusions.
I apologize for such a long post.
2) There is a similar discord [from my perspective] in the aquarium community regarding the correlation between higher nutrient concentrations and algae. While the scientific community acknowledges this link, the aquarium community has taken the view that there is no causal relationship between nutrients and algae. However, from my point of view, this is again comparing apples with oranges. This inconsistency seems to me to be due to overlooking other factors that play a role in this (especially the preferences of different algae species with respect to water parameters, light, temperature, pH, redox and optimum nutrient concentration). For example, it has been confirmed to me several times in my experiments that green haze, for example, is much more likely to occur [under certain conditions] in acidic water, whereas bacterial haze or green filamentous algae is more likely to occur in water with neutral pH. Just change the pH and you can be done with the problem. But I mention this only as an example of how little we know about the actual causes of some things/problems, and how often we cling to an opinion without considering other possibilities.
3) I also agree with @Art that nutrient availability and [related] environmental stability certainly plays an important role. If only for the reason that plants adapt to any changes in the external environment (e.g. by activating or deactivating various mechanisms that result in various metabolic changes, etc.), and some of those adaptations are quite exhausting for them. For example, if plants have a steadily higher CO2 concentration (say 10 ppm) available to them, then carbon uptake is so energy-inefficient that it saves them a lot of energy that they can spend on things other than carbon acquisition. However, if they don't have enough CO2 available and are forced to resort to carbon extraction from HCO3 (if they can do that at all), then they supposedly use so much energy to do that that they [or some of them] then need illumination of at least 80 µmol PAR to maintain a positive energy balance. And there are certainly many such examples where one is related to the other.
4) Regarding the optimal ratio of nutrients and their absolute (specific) concentration, I think there is again a considerable discord here, where every aquarist has a different opinion. One of the few things we can hopefully all agree on is that plants take up different nutrients in different amounts, with the greatest demand [ignoring water = hydrogen and oxygen] being for carbon and then nitrogen. The other nutrients they need [compared to these two nutrients] in much smaller quantities. And while the specific optimal ratio of most nutrients is fairly well known for terrestrial agricultural crops, not many people have investigated this for aquatic plants. In general, the optimal Ca:Mg ratio tends to be in the range of 2-6:1. However, many things may be different for aquatic plants because aquatic plants are surrounded by nutrient solution, so most nutrients are "passively pushed" into them and they do not have as good a means of regulating their uptake as terrestrial plants, where most nutrients are bound in the soil and the plants have to "actively extract" them when needed. This suggests to me that the optimum nutrient ratio may play a much greater role in aquatic plants than in terrestrial ones, since here the internal balance of charges can be upset much more easily by an inappropriate nutrient solution. However, it should certainly be borne in mind that many plants may be better adapted to these problems than others. But here again, I think that many (perhaps most) aquarists often focus on nutrient ratios without considering other factors that may play a role. For example, think about how many aquarists include such a trivial parameter as pH or redox (water/soil) in their tank journals. Virtually none. Yet I consider both of these parameters to be crucial, as they have a cascading effect on a whole host of other things (from nutrient availability to microbial composition). Another thing that is often overlooked when considering optimal nutrient ratios is the fact that most essential nutrients (including calcium, magnesium and potassium) are present in some quantity in organic sediments. And while the prevailing opinion in the scientific community is that most aquatic plants prefer to take up these nutrients from the water column, this may be far from being true for all aquarium plants. In other words, whatever concentrations of Ca:Mg:K we have in the water, these concentrations may be in completely different ratios and concentrations in the sediment, and if [at least some] plants can obtain these nutrients in adequate amounts from the sediment as well, then this may distort the overall picture, and knowing their exact ratios and concentrations in the water may be of little use ... because we are again overlooking another factor (= sediment).
My point here is to show that, while I welcome discussion of these matters, I think (and hopefully have managed to present some meaningful arguments for it) that unless we learn to evaluate the phenomena that take place in our aquaria in the broader context of all the relevant factors that may have a major influence on them, we will hardly reach any meaningful (generally valid) conclusions.
I apologize for such a long post.
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