M
Marcel G
Guest
I think this is not true in the case of CO2. The authors of the above study say that saturation point of free CO2 was 0.5 mM (= 500 µM), which is 22 ppm ... and the half saturation point 150-170 µM, which is 6.6 to 7.5 ppm. This is the concentration measured in the water, rather then an amount the plants actually used up. So if we want to have an unlimiting CO2 level in our tanks, we need no more then 20 ppm (actually much less as we don't have 1000 µmol PAR nor 30°C most of the time, and we don't have tanks where 100% of plants are weeds). If our dropchecker says we have 20 ppm we may "rest in peace" (and even with 10 ppm all our plants should do just fine) as it means that this amount of CO2 is already dissolved in the water ... so there's no need to worry much about good distribution ... as long as we have some flow, the CO2 should get to all our plants. So as I already mentioned, the uptake of CO2 is limited by slow gaseous diffusion; even if we raise CO2 concentration in our tank (to more then 20 ppm), our aquatic plants will be still limited by the slow gaseous diffusion. So as I understand it, when plants have 20 ppm of CO2 dissolved in the water, the rate of gaseous diffusion reaches its maximum potencial. And again: This applies to fast growing weeds under extremely strong light and high temperature! In normal (average) conditions of our planted tanks, we never ever meet such a conditions.
On the other hand, high (= totally unnecessary and highly unlimiting) levels of some nutrients (e.g. PO4 or CO2) may have negative effects on some kinds of algae. So if I have a high level of nutrients in my high-tech tank, under normal conditions I would suffer from algae (after couple of weeks, and without regular maintenance and some algivores). But if I raise the nutrient concentrations to some extreme levels, it may suppress algae. But it's a mistake (IMO) to make some general conclusions that high level of nutrients pose no risk for me in regard to algae (but that's another story).
So in my opinion, the people who are driving their nutrient levels to extremes (50-70 ppm CO2, 30-60 ppm NO3, 3-10 ppm PO4, 1-2 ppm Fe) are not good horticulturalists but good algae killers. They are making a dangerous and poisoning environment for algae ... that's all. If you get too much light, it will burn you. If you add too much nutrients into your tank, it will create an environment hostile to lower life (like algae). That's my hypothesis.
On the other hand, high (= totally unnecessary and highly unlimiting) levels of some nutrients (e.g. PO4 or CO2) may have negative effects on some kinds of algae. So if I have a high level of nutrients in my high-tech tank, under normal conditions I would suffer from algae (after couple of weeks, and without regular maintenance and some algivores). But if I raise the nutrient concentrations to some extreme levels, it may suppress algae. But it's a mistake (IMO) to make some general conclusions that high level of nutrients pose no risk for me in regard to algae (but that's another story).
So in my opinion, the people who are driving their nutrient levels to extremes (50-70 ppm CO2, 30-60 ppm NO3, 3-10 ppm PO4, 1-2 ppm Fe) are not good horticulturalists but good algae killers. They are making a dangerous and poisoning environment for algae ... that's all. If you get too much light, it will burn you. If you add too much nutrients into your tank, it will create an environment hostile to lower life (like algae). That's my hypothesis.