On the "morning after" photograph, there seems to be a surface film.
How much DIY CO2 is being generated? If for some reason the DIY system is highly active, you might be getting some sort of acidic reaction. You can almost certainly improve over-night water quality by using some method of aeration at night, at least for the short term. Another idea might be to disconnect the DIY CO2 overnight (if you decide to do that, you will then understand the convenience of solenoids and pressurized CO2 systems).
Andrew Cribb
How much DIY CO2 is being generated? If for some reason the DIY system is highly active, you might be getting some sort of acidic reaction. You can almost certainly improve over-night water quality by using some method of aeration at night, at least for the short term. Another idea might be to disconnect the DIY CO2 overnight (if you decide to do that, you will then understand the convenience of solenoids and pressurized CO2 systems).
Andrew Cribb