I used a co2 scrubber in the past but gave up on it because the media was lasting 2-3 days and was costing $30 a month in media. I read the media will last way longer if you connect one side of the scrubber to the skimmer intake and the other to the top of skimmer cap, so it will recirculate the scrubbed air. I was always paranoid to do that because if my skimmer overflows it will just suck up into the media and go into my tank. I finally got tired of low ph (mine was same as yours) and wanted to try the scrubber again but this time I set it up the way I was scared to do. I have my skimmer drain into a bucket in case it overflows so it wont go into the media. If you have an apex and can put a float switch in the skimmer lid to turn off the skimmer. I am using a different media this time and it seems to last about 2 weeks before I have to switch the media. I am not sure if it last longer because of the different media or because I have the scrubber plumbed differently.
For what it's worth I believe my systems growth is better with a higher ph and I won't run a system again with low ph.