[RTR]

There is absolutely no problem with eye-balling. Most experienced hobbyists use it the large majority of the time, and do so because it works. Novices don't yet have the educated eyes, so need alternate pathways.

I have only long-term operated one tank with supplemented CO2 where I needed to supplement KH (office 55, very different and much softer river-source water supply) I used a spare smallish external canister (Eheim adicts have spares). I used mesh bags of what was then Caribsea's coarsest aragonite substarte, with a bit of coral rubble added. The tank bags were traded out every few weeks for rinsing, drying, re-rinsing and back in to use. The aging reservoir bags were handled the same.

I had an office closet available, so was able to age my water there much as i do at home. Tap water was used to fill a caster-mounted Rubbermaid food-safe Roughneck with a circulation pump and glass strip with a heater for at least 48-72 hours, usually the full week between partials. There was a "blind" (unpowered) canister body in the circulation line, loaded with a similar bag of aragonite/rubble mix. This brought the partial water almost up to tank levels before it was used in the tank, and the small canister on the tank only had to bring the KH up a tab and hold it there. The tank was quite stable. Planting was quite heavy, but fewer stems than you use (lazy aquatic gardener). Lighting was staggered, moderate early and late cycle, only "high" for the middle half of the daily cycle Pearling was not obvious unless I killed the two internal circulation pumps just to show supersaturation.

As an aside, I am not a fan of 'effervescent' tanks. Oxygen saturation is certainly good and likely beneficial. Supersaturation and fizzy water bugs me. I am a current nut, so I am not generally bothered with excessive bubbles in the water column. But I am not convinced that I need high CO2 levels for pearling. Even my home, all moderate-lights tanks, do show pearling if I reduce the current, without CO2 supplement. But again, none of my plants require high light intensities or high nutrients for normal growth and metabolism. That is just not my personal style.