If I may tag-along with a question for Tom (and forgive me if my paraphrasing is wrong): You recommend minimal water changes with non-CO2 so as to avoid algae-inducing spikes in CO2. Does the same caveat apply if using remineralized RO/DI for changes? I've often read that high CO2 levels in tap will deplete a DI resin rather quickly so my assumption has been that it's removing it. Or would water pick up enough just sitting so as to make it that much higher in CO2 than we'd find in a planted aquarium with no added gas?
CO2 is not a salt, so I see little way for the DI/RO to remove it, but I could be wrong.
Not a lot you can do about it unless you want another holding degassing reservoir
I'll pass on that. Usign RO is a PITA enough, but if you set up a larger holding tank and a nice auto fill set up, this can be minimal labor and effort, problem is, most do not or cannot set this up like that.
For a 20 Gallon tank, not worth it, but for a 200 Gallon home display? Certainly.
I do not think anyone in their right mind would bother using RO/DI and doing frequent water changes for a non CO2 or an Excel type tank(Excel: most of which are smaller tanks anyway). There are a few cases where doing this might be useful, eg, Discus tank with lots of floating plants.