hoppycalif

A complication with Liebig's law of the minimum is that different plants have different needs for nutrients and light. If we had nothing but one species of plants in our tank it would be possible to adjust everything so we would get the maximum growth, with no leftover nutrients to feed algae. Maybe this means we shouldn't put anubias in the same tank with Amazon sword plants.

mistergreen

We can put low light plants in with high light plants, mainly in the shade of the bigger plants.

Dude

This makes me wonder what plant would have the most genetic potential for fast growth. Say someone cranked everything up to 11 (lights, fertilization, and CO2), what is the biological limit of growth for various plants? Surely it has been done before. In my own limited experience in much more modest conditions I've observed some plants growing several inches per day.

mistergreen

Yup, there are weeds that grow very fast like hornwort, elodea, H. Polysperma.

Seattle_Aquarist

Hi All,

I'm not sure I totally embrace Liebig's Law, there have been several cases I have seen where more than one nutrient was effecting healthy plant growth. I would be more inclined to say that there is usually a primary cause and likely secondary causes.

As for the EI Method it does provide a surplus of all three macro-nutrients (N, P, K), and if the pH is correct (i.e. below 7.0) sufficient ETDA iron, but very little of the other secondary nutrients magnesium, and no calcium whatsoever. It does contain manganese, boron, zinc, and molybdenum.

Living in the Seattle area our water if very, very soft and has 9 ppm of Ca and 0.6 ppm of Mg, if I don't add additional secondary nutrients to my tanks my plants just don't grow. -Roy

hoppycalif

I think it isn't that some of us don't embrace Liebig's Law, but that we just don't understand it. I find it hard to grasp, as simple as it is. There is certainly a lot of evidence to support it. One good example is CO2. Before people used CO2 with their planted aquarium they tried to get good plant growth by just getting more intense lighting, which is understandable because there were few ways to get more intense lighting - incandescent bulbs and fluorescent bulbs were the only choices. When we heard about using a yeast/sugar mix to get CO2 into the water it was almost miraculous. It always caused the plants to grow much faster, with whatever lighting we had. That was because carbon was the nutrient that was least available to the plants. The Walstad method worked so well largely because it used CO2 generated by nature to increase the amount of carbon available to the plants.

I think there is a benefit to trying to think about Liebig's Law as we figure out how to make out aquatic plants grow. Of course it isn't the magic bullet, but it is still important.