The fact that there are little or no phosphates may very well BE THE REASON there is hair algae. I'm not saying this is definately the reason, because it could be many other factors as well, like too much iron in the water, etc. I'm just saying that plants need phosphorous as a "macro nutrient", and with all the other nutrients lying around in the water, SOMETHING's going to use them! The plants need phosphate to use many other nutrients effectively. For instance if I have zero phosphates in my water, my nitrates tend to stay at an elevated level. The way I drop the nitrates is by ADDING phosphate! Weird, yes,.......but balance is everything.
