Low pH

[Abarnes]

Mag at 1290 is fine, I wouldn't have it too much higher, as long as it is in balance with Calk and Alk.

[Black X]

Started adding Kalkwasser to the ATO again and my pH has risen and Alk dropped slightly. So I am guessing that my ratios must have been slightly out and my corals stopped taking on Alk.

[Tone]

Don't bother worrying about pH ... good ventilation, decent water circulation, stable water parameters and forget about chasing pH.

[Onsan]

Take a cup of tank water and put the air stone in that for 1/2 hour or so and then take a pH reading.

Take a pH reading of the tank. Put some tank water in a cup and aerate it for 1/2 and hour, then take a pH reading of the cup water.

Chris

Do that, but do it outside in the open air.

If you have your house closed up due to winter/keeping the heat in, this could be raising the CO2 in your house. Do what Chris said outside and you'll identify if the issue is from the air inside the home.

I had issues previously with CO2 depressing pH, the issue was due to the CO2 levels inside a poorly ventilated house. In summer all windows and doors remain shut due to a/c used to cool the house, this raised the CO2 level in the house which raised the level of dissolved CO2 and depressed the pH.
Solution was to relocate the skimmers air feed tube through the window into fresh air, problem cleared up in a bit over an hour.

[Brett240]

PH drops to 7.9 at night.

that's a completely acceptable level at night. any reason why that's bothering you?

[Ageofaquariums]

Time for some CDX co2 removal media!

[Black X]

I was thinking 7.9 is starting to get too low.

[Brett240]

if it is i'm in trouble. that's what mines at, though the tank doesn't seem to care.

[Autonomy]

Low pH: Causes and Cures by Randy Holmes-Farley
http://www.reefkeeping.com/issues/2004-09/rhf/

Definitely a very helpful read when wanting to understand the following further:
- What is pH?
- Why Monitor pH?
- What is the Acceptable pH Range for Reef Aquaria?
- Carbon Dioxide and pH.
- Why Does pH Change During the Day and Night?
- Solving pH Problems.
- Causes of Low pH Problems.
- The Aeration Test.
- Solutions to pH Problems.
- Low pH due to CaCO3/CO2 Reactors.
- Low pH due to High Indoor Carbon Dioxide Levels.
- Low pH due to Low Alkalinity.
- Acute Downward pH Spikes.

[Aydee]

Quick obvious question:
Have you tested the tester?
Old/dodgy test kits do exist.
PH meters can get out of calibration.

Perhaps test it with RODI water. It should be pretty close to 7. (Maybe a little on the acidic side).

Dave