Active Reefer
Manhattan Reefs
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First of all. A lot of good advice here already.
Let me add mine.
Get another ph test to verify the apex is correct (not api kits). Otherwise you are chasing your tail. Apex ph probe are not the best. The probe are prone to electrical interference if probe cable is too close to high power cords and it will be off.
Open windows does and will work. Running skimmer like outside does work. If your building have no air movement. Put a fan in the window to get fresh air into the house. Give it two days for ph to raise. You won’t see a change in 5 mins.
Simple test you can do. Take a cup of tank water and let it sit out doors for an hour or two. Take a ph reading. If it goes up than you know you house have high Co2 concentration.
Dosing kalk will bring you your ph but it will bring up your calcium and alkalinity also. Becareful!
If your coral and fish are ok. Stop chasing ph!