I'm still a ways away from doing it critically.

But the question is rather interesting even though the "circulation/dissolving" statements elucidated thus far are correct I'd say.

But it's not why your HC is not growing, it's still a CO2 issue.

The client had issues because he kept meddling with the tank, then neglecting it for a period and then the CO2 would run out and he'd not check things for several days and there's about 8-9w/gal on the tank.

So that's not exactly a good case study
He's getting U gramifolia in place of it and has threatened to add Gloss(shudder)

Regards,
Tom Barr