Does top off water drop PH?

[Malibu361]

I have an ATO with just RO/DI water and my buddy was telling me that it will drop my PH .Is this true? If so, should I add something to the top off water ?I notice my PH always fluxuates so now that he says this it has me thinking..any feedback? Thanks ...

 

[tosiek]

The drop that it could cause is not severe enough to cause worry. Only way your going to notice your PH drop is when your doing like a gallon or more into a 20g tank. And even then the drop rather small. Your tank fluctuates during the night/day cycles as bacteria tends to grow with the lights on. My controller has been reading 8.0 at night and 8.25-3 during the day. So, if your taking a PH reading in the morning it will read different than at night. I do know poeple that PH balance their top off water, but thats mainly to add some calcium or alk into it to make up for loss during growth because they are not adding suppliments daily. Alot of people keep their fuge light on during the night and alternate with the lights in the tank to make up for PH swings.

if your ATO is slowly topping off the water during the day thats probably not the cause of the PH fluctuations. Most likely they are from the night/day cycles. And unless they are swinging from crazy numbers like 7.5 to 8.4 i wouldn;t worry. How do the coral look?

 

[Malibu361]

Everything has great growth and is nice and healthy the number arent that crazy usually 7.9-8.2ish .....Thanks

 

[salt-rookie]

An ATO should replace the evaporated water in real time, and should have NO effect on the pH. Only pure water evaporates at an assumed pH of a neutral 7.0. The incoming RO/DI water should be very close to that. Replacing it in small amounts in real time eliminates what you should really fear...HYPO or HYPERsalinity.