You have already got a lot of good responses Flame and the only thing I can add is that flow through I believe also makes a difference.
In my pond if we have a relative dry year where the water recedes from evaporation the nutrients are concentrated and I believe I have more problems in that situation. This year we have had numerous large rain events where a lot of water runs out the overflow and the water is staying a lot better looking.
Of course that flow through water also can be loaded with nutrients or not so much so. If we have a big rain event in late spring after fertilizer has been applied on ag ground, there is likely quite a bit of nutrients in the runoff. Phosphorous in ag fertilizer is generally considered stable and once attached to soil particles becomes immobile (unless of course the soil itself washes into the pond, in which case the P2O5 is also there). But there is a very small percentage that is water soluble and can move with the water. Nitrogen comes in different forms and the soil naturally turns organic matter into nitrogen through biologic activity. So at any particular time there could be little N moved with the water or a lot.
So flow through water could be helping with reducing nutrients or also could be adding, just depends. But generally speaking my water stays a lot better looking when I have some regular flow through.
No specific answers to your question. Just my observations as I am learning just like you.
Last edited by snrub; 09/17/16 08:37 AM.
