Personally I do not understand why people are so reluctant to admit that phospates may be related to algae. Does it make it a sin? There is plenty of evidence in science literature (papers regarding natural aquatic habitats, practical knowledge on water treatment, media used for cultivating algae in laboratories, etc.) that IMO is much more reliable, transparent and objective than:
- scientists' conspiracy theories (do you really think scientists do care about this? Do you think that all the scientists, paper reviewers, laboratories and a very long etc. in this world are aligned to cheat on us? Come on, algae blooms are not strategic to rule this world. I can believe that a company whose incomes depend on algae cleaning can say so, but the whole international scientific community?)
- personal experiences on tank management in which parameters' control is very difficult, do not have accurate measure equipment, reliable methdologies, repeated samples, etc.
- internet forums
I am not saying it is the absolute truth and that the rest is faulse, but I am careful enough to admit that it makes a lot of sense (even being aware that everything has not been answered yet and that others' opinion makes also sense). I try to be open minded, that's all.
So once again, I would say that
there is quite a lot of evidence to say that phosphate may induce algae BUT hobbyists do not have to fear phosphates in a planted tank, as they are necessary for plant growth (at least in high light conditions) and they do not lead necessarily to algae.
Why adding phosphates do not necessarily lead to algae blooms? There is probably more than one reason. I like Darrel's approach on different posible "stability areas/proper configurations" in the CO2-PAR-nutrient triangle, I like the allelopathy theory (not sure if it is right) and I like the "anti-algae" approach (algae need time to grow and don't like to be disturbed -as any other organism. Our tank maintenance (WCs, scraping glass, removal of dead tissues, etc.), equipment (filter, flow, distribution, etc.) and animals (grazers) don't give algae the time to develop. Think about it in the opposite way, what about trying to grow aquatic plants in a tank with herbivore fish, no filtering, no WC?... not imposible but certainly much more difficult, right?
Probably none of them by itself is enough to explain why high nutrients tank can be algae free (I'm probbaly missing some more), but it looks quite reasonable that in high nutrient tanks our behaviour/approach/setup/configuration/plant healthiness/equipment has a huge influence for keeping algae under control. It may sound weird for a beginner but we can cope with high nutrients levels as long as we can keep planted tanks in good conditions.
Merry Christmas to all of you (with or without PO4)
Jordi