Pink slime!

[waterbear]

Thanks chem geek.

Taken what you and waterbear have written, I can conclude that the pH stability was borne from stopping my waterfall and by tamping down the ontime for my SWCG -- two causes for pH rise.

And the second reason is why the CYA should be at the maximim since it will mean that a lower on percentage will maintain the desired FC level. Lower on time means less aeration means slower pH rise.