I'll second the above regarding PO4. My plant tank is only about 2.5
months old, and save for some greenwater at the beginning and trace
amounts of green-spot algae now, the tank has been algae-free - and I
intentionally attain PO4 levels 2ppm! (My tapwater is ~3ppm in PO4)

Hmm, I always understood that high PO4 was a contributor - especially for
BBA but I'll take your word for it!


I'll second the above with respect to KH, too, assuming no CO2
injection. Simply put, the only thing that affects, if one is not
using CO2, is the pH. And that's just not a big deal for algae.

True enough

KH can possibly matter if one *is* using CO2, though. Then, KH
determines [CO2] at a given pH

Kind of the wrong way round I think. Perhaps better put that at a given
level of Kh then Ph varies depending on the level of CO2 in the tank.


I.