The Algae
Algae is one of the "pest" reefers tries to control. How to deal with excessive algal growth in the aquarium? This is one of the challenges which many reefers face.
The conventional wisdom (if you read through my posts, you will know I'm not a fan of blinding believing in them)is that, one must tackle the algae problem at its source. By addressing the underlying nutrient problem, we can overcome the algae problem. To many, this means reducing nitrate and phosphate in the water.
I, however, think that this view is missing out on the bigger picture.
Algae in the Reef
Just like the corals, algae evolves to take advantage of the sun light, and produce their energy supply through photosynthesis. At the same time, they require inorganic nutrients such as nitrate and phosphate in order to build its biomass. So, suppose if we can deny the algae of these nutrients, by lower the nitrate and phosphate to very low levels, surely we can control the aglae growth, right?
It's not that simple. Unfortunately, algae evolved to take advantage of the environment where coral thrives. They can survive, and thrive, even under very low level of nutrients, such as that of a coral reef. So in the blind rush to drive down the nutrients, one often realise that the first to suffer is corals, not algae.
Therefore, dealing with algae by driving down nutrients, is probably not the best direction.
Algae NOT on the Reef
Having said all these, we are face with another interesting fact: natural reefs are not overrun with algae. This is not because algae cannot grow in the reef, but because herbivores residing in the reef place a grazing pressure on those growth. Tangs, foxface, angelfish and various inverts continuously prey on the algae, and keeps the population from overrunning the reef.
Therefore, the key to algae control is having a sufficient population of herbivores. And that's the natures' way to keep algae in check.