Precipitation is more for concentrated doses. Like in a dosing bottle. The dose you make at the beginning of the week is comparatively weak, especially when you consider the entire volume of water in your tank.
As for fish/invert health, I don't have any links to fall back on but I have seen many threads that do discuss this and the consensus is that the Nitrates from Ferts don't have the same effect that Nitrates from decomposition have. Probably due to the lack of dissolved organics and other material present when you have decomposing matter.
Plus you are only adding in 20ppm, give or take a few and depending on your targets. I follow tanks that hit close to 50ppm without ill effect to inhabitants. I myself have a low tech neo shrimp tank that hovered around 50ppm nitrate for awhile before I figured out my son was dosing too much Ferts. We had a batch of babies during that time. Go figure.
@Tom558 My algae production went down when I started front loading. The tank pictured now goes over 2 weeks before I see algae on tank sides. And during summer months it gets roughly an hour of direct sunlight a day. Keep in mind it's probably not due to just the front loading but it definitely doesn't hinder the process.
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