Putting a light over some water is the single greatest algae trigger, Chri$, with the word trigger being the key. This is why some people are growing their plants on just damp substarte to allow them to become established, before adding water at a later date. The water side of the trigger has been removed. Other triggers are persistent ammonia levels, even levels undetectable by our test kits, and poor CO2.
Keeping phosphates and nitrates low in a tank with zero plants will still not control the algae. Most people have sufficient nutrients in their tap water to feed huge algae blooms, yet they don`t have algae problems. This could be down to the fact that fish only tanks don`t generally have the high lighting levels of a lot of planted tanks.
Trying to control algae through depriving it of nutrients is virtually impossible due to the imperceptible levels of nutrients it can thrive on (RO water).
Ammonia and phosphates will feed algae, but they will not trigger it. Ammonia and too much light in fish only tanks could well be the major causes, but I tend to look at things from the planted tank point of view where CO2 is generally the big variable to trigger algae.
Exactly how or why algae uses or detects these triggers is an unknown, but poor plant health, accompanied by the ammonia they start leaching, is a major trigger also. I have read people on this forum saying brown algae only thrives in low light conditions, but I have seen it appear in all three of my high light tanks. In my experience, the diatoms are the first to appear in my new tanks.
Dave.
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