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Originally Posted by dwalstad There are plenty of river and oceanic algal blooms due to nitrate and phosphate pollution that would contradict a blanket statement like this.
Although algae (like aquatic plants) prefer ammonia to nitrogen, algae can grow very well with nitrates alone.
Some of the cyanobacteria (blue-green algae) can actually use atmospheric nitrogen for all their nitrogen needs.
In aquariums due to the fishfood input, there's generally an excess of all nutrients. Iron being much less soluble than other nutrients can, in this situtation, limit algal (see my book, pages 169-170).
What stimulates algae depends upon the situation. |
I guess the statement should be qualified:
He said that (assuming your tank is full of healthy plants) excess nutrients (NPK and traces) don't cause algae but excess ammonia (NH4) does, and he's right.
That certainly fits with my experience. I can have 30+ ppm NO3 and 4 to 5 ppm PO4 and if my plants are happy I have virtually no algae.
I think you're right though that it depends on the situation; in a tank without plants algae can gain a foothold easily.