01-26-2013, 12:11 PM
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To answer your question, the pH swings may be caused by CO2 buildup within the tank which is why RM suggested aerating the tank. You can determine if CO2 is the problem by aerating and testing the pH throughout the day (especially right before lights-on and right after lights-out) and comparing the results to what you get before aerating. If you're no longer experiencing that pH swing, then it was caused by CO2. However, this won't work if the CO2 is building up within the air because the purpose of aerating is to bring the water and air back into equilibrium; so if extra CO2 is in the water, aerating will strip the CO2 out, but if there's more CO2 in the air then in the water, aerating will bring CO2 into the tank and make the problem worse.
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