What is acceptable PH drop at night?


New Member
I have a 29 gal bio cube.Just added a aqua fudge refugium to back of tank
(2.5) gal. I have reef set up with alot of live rock.I have two clowns ,fire fish and royal gamma. I run reverse light at night.
Kh is 214 ppm
calcium is 480
nitrates,amonia,phosphates 0
My question is my ph at end of day is 8.2 in morning its 7.99
Is this ok
I added buffer which raised the KH and calcuim and cant get the ph higher without raising the other levels to high.
Is the tank too new(only two monthes)


Expect a PH a drop at night time. Its a normal thing. Usually people keep a refugium tank and have the lights on that at night time when the main tank lights are off to balance it out to avoid the drop. I dont know the reason so this is where I stop. You should be safe with that IMO.


New Member
I will do reverse lights and let fuge mature a little see if that helps.The only other thing I heard was the o2 level.I have a closed hood and started leaving open at night.Im wondering if airstone will help to stable.


I am very new to saltwater, but isn't bubbles in a tank a bad thing? (in saltwater of course)

florida joe

Well-Known Member
Simply stated
When our aquariums are illuminated photosynthesis takes place, this photosynthesis uses up carbon dioxide which is generated by all organisms in our tank. When carbon dioxide levels fall ph increases. When we turn off our lights the carbon dioxide is still produced but there is no photosynthesis to consume the carbon dioxides so our ph drops.
Note ph is a measure of hydrogen ion concentration in solution .In our reef tanks we tend to have high rates of photosynthesis so our ph may drop below 8.0 and rise to above 8.5 with out any reverse lighting. You would not want your ph to drop below 7.8 or above 9.0
In our reef tanks I believe the best range for calcification is between 8.2 and 8.5
As far as o2. Oxygen enters our tanks via air water exchange and photosynthesis. When we turn off our lights there is no photosynthesis so we only have air water exchange to introduce o2 (unless we are using an external injection system) hobbyist with hoods tend to leave them open at night to add in the exchange .
This is a simplified explanation but I hope it helps


New Member
Thanks for the info,I think Im getting it figure out.I left hood open and high ph yesterday went to 8.26 low was 8.09 see what happens today.Im going to work on getting low end to 8.2


New Member
I know I dont want them in tank but thought about putting in fudge,I have abandoned that idea.