Measure Alk/pH in the a.m. or p.m.?

[cato]

Should Alk and pH be measured in am, pm or both and which one am I trying to keep within norm ranges. I assume the diff in readings has something to do with photosynthetic activity during the day with full lights on??

 

[iflyprops]

I was told to do it in the morning before the lights come on.

 

[cobs00]

To my understanding, PH drops at night. You might want to do your readings sometime mid day after your lights have been on for a while to get a more acurate reading.

 

[cato]

Can someone break the tie???

 

[glaudds]

I would measure both, once in the morning since that will be your lowest ph, and once at night right before the lights go off.
That way you will have a feel of what your ph swing is during the day. You ultimately would want the smallest swing possible. That is achieved many ways, one of which is to get your alk and ca at optimum levels.