An Interesting Example:

This pool/spa combo, featuring black plaster, was set up to be bicarb-started. You can see the barrel and hoses in the background. You may also notice the pole suspended across the deep end, with the pH probes… we were documenting the chemistry for this one.

When we came back that evening, the pool was crystal clear, but the spa looked like it was full of milk!

Here, we brushed the top spa step…

And here we brushed the whole spa surface. The homeowner had come home and decided to fill the spa using non-bicarbonate tap water. What a difference! Notice how clear the pool in the background is, as you look at the bench along the left curve…

Bicarb Start Laminated Card
(reprinted with approval from OnBalance)