how do you maintain Ph in reef aquaria?

Mine stays steady by using a reverse cycle on the sump and by letting fresh air circulate in the room with the tank when possible.

Same here. Reverse light cycle on refugium keeps PH steady at 8.1 all day and night.

Grins said:

Mine stays steady by using a reverse cycle on the sump and by letting fresh air circulate in the room with the tank when possible.

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Ditto on the reverse light cycle but I also dose a mixture of sodium carbonate and sodium bicarbonate to maintain alkalinity which helps with pH stability. (2 parts sodium carbonate, 1 part sodium bicarbonate dissolved in a cup of distilled water and poured directly into the sump).

Chuck

I use the same water, salt mix, chemicals and food every day and other than that don't worry about pH and it's been pretty stable for me.

I don't use a reverse lighting schedule on my fuge, either, as it hangs on the back of my tank and 'runs' off my metal halide light like the rest of the tank.

Do not worry about testing pH.
Instead purchase a Calcium test kit and an Alkalinity test kit.
Then purchase a 2-part solution for Calcium and Alkalinity supplements. I like ESV-Bionic

Test Alkalinity once every other day and calcium. Then make additions to the tank as needed.

If Calcium tests are above 400ppm you need to do nothing.
If alk test above 2.5meg/l you need to do nothing.

Only dose the supplement that is lower than the threshold limits.

This will stabilize and buffer pH naturally. Do not be concerned if it is below 8.0 during this technique. That is normal at times also.

Always do at least a 20% water change every other week.

If you have RO water get a DI unit also. It will provide better water.

This is the proper way to regulate the buffer system of the tank and will avoid precipitate issues.

i used arognite as my subsrate ...it helps keep the ph stable.