Constantly Falling pH

[vettemedx]

Hi...Just a quick question. I recently took over a well established tank cared for by a supposed industry professional. I moved the tank, let it cycle for a month with the existing live rock, sand, and water. During that time, I made adjustments to the filtration slowly, as to not throw off the bacteria count in there. I've added some inverts, cleaner crew, and a clown, all of which are doing awesome. My water levels are spot on, except for pH. Several hours after my weekly water change, my pH reads about 8.2. Within 24 hours, it drops below 7.6 and needs to be dosed. my kH is pretty stable at around 10 deg. I'm using premixed nutra water as well as topping off with RODI. Any ideas as to why this is happening? Thanks in advance.

[jedimasterben]

Are people living or working in the area the tank is in? Is the building it is in well sealed? My tank gets down there as well when I'm home and in the tank room for more than an hour or so, I can see the pH graph drop like a rock.

[downbeach]

What are you using to measure the pH? There is a mathematical relationship between your alkalinity and CO2 for your pH, meaning that is your alk, et.al. is within acceptable levels (7-11dKH alk) then the issue is with the amount of CO2 in your system and/or the surrounding atmosphere. If you're dosing a pH buffer, I would stop, since the elevating affect will be temporary, with the pH returning to its base level once the CO2 has reached equilibrium again, leaving you with elevated alk. Are you getting good aeration in the system, i.e., a skimmer with the system, good water surface movement? If so, you will have to introduce a better quality(less CO2) air source, i.e. running an air line from your skimmer air intake to an outside air source, open some windows, etc., adding a CO2 scrubber(expensive media), or do something to take up the excess CO2, i.e. ATS, Fuge, etc.

[oseymour]

What do you mean by "it drops below 7.6 and needs to be dosed?" - please stay away from PH buffets, the tend to cause issues over time.

If your Alk/Kh levels are fine then it's probably CO2. My family of 4 in an NYC apartment and when winter comes and we can't open the windows my ph drop to those levels too. I had to add a CO2 scrubber to my skimmer intake.

You can also use kalkwasser but I already had my 2 part dialed in and was hesitant to mess with it.


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[vettemedx]

Thank you all for responding..... I am starting to think it's the CO as well. I am in an apartment. Since I took the hood off the tank and aimed the heads more toward the surface of the water I've noticed the pH doesn't drop as quickly. I've used two test kits to test the pH and kH both giving me the same results. I ran the air line from the skimmer to the outside last night, hoping for some improvement. If not i'll start to look into CO scrubbers.

[jonwright]

I really discounted the idea of CO2 in the air. After leaving a window cracked in my basement my Ph has actually resumed to being within the expected levels. I figured my basement was leaky enough but it wasn't.

Observation was believing for me.

I didn't run an outside line for a variety of reasons. I also tried a CO2 scrubber and it is another thing to mess with. I have to replace it in a large reactor every week or two (that is adding up with more $$ and time/effort/focus). Plus it had large Ph swings that I didn't like on the tank when I replaced the media once spent. AAAnnnndddd...took the Ph too high (IMO).

Once I quit messing with the scrbber and just left the window cracked a little bit it's now evened out without my having to mess with it. Plus my dehumidifier isn't on all the time, either.

[vettemedx]

It's been a few days and i'm seeing big improvements already