co2 and algea

[newplant]

Can someone explain to me why co2 prevent algea from growing. If one doses EI there will be plenty of nutrients in the water + high light but why algea won't grow. It is also often said if plants are well established algea will be less of a problem, why?

[RyanRX7]

The idea behind it all is that the plants are provided enough nutrients that they grow at or close to the best rate possible. In turn they use up the nutrients before the algae gets a chance to.

[newplant]

Originally Posted by RyanRX7

The idea behind it all is that the plants are provided enough nutrients that they grow at or close to the best rate possible. In turn they use up the nutrients before the algae gets a chance to.

Not sure if I agree to the logic. Algea will have access to the same water with the same nutrient, won't it?

[mscichlid]

And the key is to attempt to keep your tank in balance to curtail the algae's dominance.

[Storm]

There have been a lot of studies done on allelochemicals. These are chemicals that plants produce that can suppress the growth of other plants. The general consensus seems to be that healthy, fast growing plants produce enough allelochemicals to inhibit algae growth. On the other hand, algae is well adapted to growing in low light and nutrient poor conditions, so if you let it get established and your plants are weak, the algae itself can produce allelochemicals that inhibit the growth of plants, killing them. Not only that, algae on the leaves blocks light starving the plants.

So, adding Co2 simply removes the carbon limiting growth factor of plants, allowing them to grow healthy and fast enough to produce enough allelochemicals to inhibit algae growth. It's like chemical warfare between plant species.

Note: this also explains why some types of plants just won't grow in a certain tank. The plants already established might be producing allelochemicals that wipe them out, or maybe the water chemistry is not favorable for a certain type of plant.