Ph levels during tank cycle

[p7willm]

I understand that Ph levels will vary night to day because plants lower CO2 during the day, however I am just starting to cycle a new tank with nothing in it but sand and reef saver dry rock and the Ph goes down, 8.02, during the night and up, 8.15, during the day.

The tank has been together for about a week and the wave in Ph is becoming more pronounced.

Ammonia is just starting to build and there are no nitrites yet.

Is this normal? Is it caused by the bacteria building up?

It doesn't appear to be light related since it bottoms out at midnight and then starts to rise steadily until 10AM, holds steady until 2PM then drops steadily. The low only lasts about an hour.

 

[brandon429]

Two clues stand out for your tank

What is the source of the ammonia, some proteins have to be added to get the ammonia you see (did the rock have prior life stuck to it, that when rehydrated is now rotting?)

-how do we know the reading for ph is accurate, is this calibrated probe reading


This thread states when a cycle is finished, how to know and what time lines are expected
http://reef2reef.com/threads/new-ta...d-cocktail-shrimp-live-rock-no-shrimp.214618/

It's handy to know ph isn't a critical cycling param but this is a great time to validate measures/eq and begin learning your tanks dynamics. You'll find cycling 33% easier if you ditch the nitrite testing altogether and sell off the kit on eBay.

 

[p7willm]

The rock is definitely dry and dead. The ammonia is coming from rotting food I have been adding to the tank.

The Ph readings come from a new Apex system with a new calibrated Ph probe. Even if the probe is calibrated wrong, I was pretty careful when calibrating and it is fairly simple, I am still getting the day/night swings.

I am not worried about what the Ph levels are I was just wondering why they were swinging. In fact if I had not setup the Apex I would have no idea what the Ph in the tank was. As far as nitrogen testing I am only looking for the levels to rise and then go down again, not really interested in what they are.

 

[Randy Holmes-Farley]

Maybe your home has more CO2 at night, or there is some photosynthesis going on from algae and cyano that you may not yet see. :)