The $20 has arrived
90 % of all pH issues are high indoor CO[SUB]2[/SUB]. It goes like this, you breath in the room, have AC or furnaces on and all release CO[SUB]2[/SUB] into inside air making it much higher than it should be unless one has a HVAC system in their house. In short, your house is like a balloon and is filling with CO[SUB]2[/SUB] and that pressure crated by that CO[SUB]2[/SUB] pushes CO[SUB]2[/SUB] into your reef tank water lowering the pH.
Examples:
CO[SUB]2[/SUB] + H[SUB]2[/SUB]O --> H[SUB]2[/SUB]CO[SUB]3[/SUB] or CO[SUB]2[/SUB] + CO3-- --> HCO[SUB]3[/SUB]- = Low pH
On the other hand, on some occasions, the same reactions take place even if there is not high room air CO[SUB]2[/SUB]. This is from over feeding or poor gas exchange at the surface or a combo of the two.
It is not just an outside test but a outside test and inside room air test. When you vigorously aerate water the CO[SUB]2[/SUB] leaves and those reactions are in reverse and the pH rises.
Test steps:
First, What is the pH, Alk, temp and Sanity of the tank, so I can calculate x, y and z. ?
1. Take a tank sample and aerate the crap out of it for 4 hrs in the tank room to see how much the pH rises.
2. Take a sample out side and do the same.
Some theoretical example tests : pH 8.2, S= 35 ppt, T = 25C, Alk, 2.25 meq / l
Example 1
Tank pH 7.8 + # 1 and the pH goes up to 7.9. We have slight tank CO[SUB]2[/SUB] issue
Tank pH 7.8 + #2 and the pH goes up to 8.2. We have a high room air CO[SUB]2[/SUB] mostly.
Example 2
Tank pH 7.8 + # 1 and the pH stays at 7.8. We have high room air CO[SUB]2[/SUB] only
Tank pH 7.8 + #2 and the pH goes up to 8.2. We have a high room air CO[SUB]2[/SUB] only.
Example 3
Tank pH 7.8 + # 1 and the pH goes to 8.2. We have high tank CO[SUB]2[/SUB] only
Tank pH 7.8 + # 2 and the pH goes to 8.2. We have high tank CO[SUB]2[/SUB] only.
These tests have nothing to do with oxygenation, it is just aeration. Aeration does two things lowers CO[SUB]2[/SUB] and raise O[SUB]2[/SUB] **usually** but not always.