I also posted this in my journal.
I wanted to find a way to lower my ph and my kh so I could house some OEBT, however I have heard weird things about using API's ph down or really any other chemical "ph down". Here are some questions I wanted to answer and I couldn't find much info online so I decided to do an informal experiment. BTW I really have no idea why I have this, it was just sitting with all my other chems.
1. How long does the it affect the parameters assuming nothing (stones, dw, etc) is buffering the water. Will it (the ph) bounce back?
2. How many drops required to lower the ph a certain amount?
I have 2 one pint jars both filled with tap. My tap ph is 7.6+ so I added ph down until it read 6.0 (4 drops). I measured kh, and sure enough the one with added ph down read 1, whereas the control needed 2. In order to make sure it's not a random occurrence I tested multiple jars. 3 jars for adjusted ph and still 1 kh. 3 jars for controls, all same results. So I think I can assume that the stuff lowers both kh and ph.
I will check ph and kh again tomorrow to see if there are any differences, as in if it's only a temporary fix. The idea is that buffering substrates will not absorb stuff forever if you change water using tap, so why not adjust the tap's kh and ph? In addition to a longer buffering soil, sensitive shrimp will not be as stressed after a water change because I'm not changing in 7.6 ph water.
I really really hope that this will end up good. So I won't have to use RO.
How I feel about non-planted aquariums.