CO2 and PH

[WhatCouldGoWrong71]

I am struggling to get my PH above 7.89 in my big tank (120G display). At night it will dip to 7.6 and during the day it will tip out at 7.89. ALK (test twice a day) 8.5 - 9.0 Cal 457 Mag 1520 (test every 4 days). So, I wondered about C02. I have a 75G planted freshwater tank that I inject CO2 into for 10 hours a day sitting 8 feet from this tank and there isn't much fresh air in this room, but it is an open layout. So I ran a line from my skimmer to outside for fresh air (about 6 feet) and there really wasn't any noticeable difference, so I guess a scrubber wouldn't make any difference also. I went an got a CO2 digital readout and sat it on top of the planted tank for days and it never went about 700. Here it has been over night (CO2 is not turned on at night). I am curious what this will read out throughout the day today.

I don't want to use a buffer. Any thoughts?

 

[Saltyreef]

What alk product are you using?

 

[WhatCouldGoWrong71]

@Saltyreef currently I am only using AFR. That tank in question is getting about 50 ML a day of AFR. You can see my test results below for the last couple weeks. As I have started to document them.

 

[Saltyreef]

You might try 2 part and use soda ash instead of baking soda