Are there any beneficial effects from Nitrate?

[AttackDonut]

Just curious. I ditched my HOT Magnum (complete with bio-beads and some old carbon) and although I've seen a drop in my Nitrates (from ~20 ppm to 0) I've seen red stringy algae (cyanobacteria perhaps?) start popping up where none existed before.

I've checked other levels and those seem fine/ Was just curious what the change might have caused and if NO3 had any beneficial effect.

[bsempel]

We've always had cyno show up when our RO filters went too long without changing... bad water... maricyn works to get rid of it..