Low pH and Alk

My tank being in the basement the pH was always on the lower side (~7.8-8.2), however I recently topped-off my Ca reactor media and after about a week I notice my pH was running at 7.6-7.8.

After running some tests I found that my alk was at 7dkh, it's usually at 9-10 dkh.

Here are my parms as of today:
ph 7.8 - Controller reading, 7.8 API test kit, 8.0 Tropic Marin test kit
Alk - 7 Instant Ocean test kit
Ca - 424 Tropic Marin kit
Mg - 1350 (bit higher than usual for my tank, usually around 1280) but I don't think this is bad.

Nitrate - undetectable
Phosphate - nothing on my API test kit but I'm getting some brown algae on the glass, overflow and power-heads.

I've been using ReefCrystals saltmix for almost 2 yrs now, the only change I made about a month ago was I bought the bucket instead of the box....that's all my LFS had.

I increased my drip rate of the effulent out of the CA reactor today, hopefully that takes care of the alk.

I do have some Pura Phoslock in a bag that I used for a few days a few months back, it's dried out....do you think I can re-use this to try and get rid of any excess phosphates? It's not bad, but I notice I have to clean the glass more often the last week or so.

 

How long has this tank been running? Have you dosed alk/ph buffer?

 

The tank is over 2 yrs old. I used buffer way back in the beginning. When my pH was at 8.2 (lights on) I didn't worry much about it because my corals were doing well. Even now that the pH is a bit lower I don't see any changes in my corals but I want to address the issue before it's too late.

 

IMO the confined space of an basement leads to reduced O2 and increased Co2 levels, causing a chronic lower pH, I am willing to bet if you ran a line out side or increased the amount of outside air to the area you would see a higher pH, consistantly.

 

Read this article:

Low pH: Causes and Cures by Randy Holmes-Farley - Reefkeeping.com

 

Yeah, I'm certain it has to do with the low O2 levels in the basement. When I open up a window the pH goes up a bit, however now that winter is almost here opening up a window for an extended period of time is not an option. The Ca reactor probably made it a bit worse with the Co2, I might have to install an exhaust fan to get rid of some excess Co2.

Thanks for the article, I remember skimming this somewhere a while back, probaly a link off of RC somewhere....