How to increase PH

[iacevedo8704]

Hello everyone, I would appreciate some advice regarding a persistent low pH issue in my reef system. I currently have a 150-gallon reef tank that has been running for about five months. The system includes a Reef Octopus Classic 150-S skimmer, a CO₂ scrubber, and a kalkwasser reactor with a dosing pump. Despite these measures, my pH consistently stays between 7.5 and 7.6 and does not increase. The CO₂ scrubber is connected to a 3/8-inch air line that draws fresh air from outside the house, so the skimmer receives external air. I am currently dosing kalkwasser at approximately 240 mL per day, but I am being cautious because my alkalinity is already around 9 dKH and my calcium is about 455 ppm. Given these parameters, I’m hesitant to increase kalk dosing further. I’m wondering if there's something I’m overlooking regarding gas exchange, equipment configuration, or chemistry that could help increase the pH. Any suggestions or insights would be greatly appreciated.

 

[Randy Holmes-Farley Verified Community Expert]

Welcome to reef2reef!

Are you sure the pH measurement is accurate? That seems a likely issue to me.

That said, this aeration test will answer that and more:

pH And The Reef Aquarium

from it:

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.