In broad terms jimbo, if you can get some plants going you'll find they will far exceed any artificial methods you might use to get everything working nicely.
As an example ... I had a half 44, oops sorry 200 litre drum out the back of my house that I keep full of water for birds and other wildlife. In the past the water was ok but slightly murky and only supporting some weak looking brownish algae. I dropped in some reeds and a water lily and while conditions in the tank aren't exactly perfect for plant growth [the the temp. hit 47.5C, thanks to global warming extremes a week back and I make no apology for making that connection] the water is always clear and might even support a few small fish, if that was my goal
. Dams respond even better.
Plants grow fast and can perform miracles!
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter
Veteran system, semi retired: 6 X 55W Solarex 12V panels; Fangpusun CC; 6 X 2V, 35 year old 550Ah lead acid flooded cell batteries.