ph swings

[EMUreef]

i for the life of my have been having trouble keeping my PH stable.

for example today i dosed my 2 part about 40 ml of alk. brough the ph to about 8.2 by the end of the day when the lights were off it was at 7.8 ish, i dosed a little more to hopefully improve the swings, went back up to about 8 ish, a couple hours later it was back down to 7.8

yes the AC is on, but the tank is in kind of a larger room. Surface agitation. Skimmers on. Fuge on reverse lighting.
skimmer air intake has a hose going out of the stand..

any other ideas?

[bigbill]

i started runing my sump lights 24hours helped a lot

[jimsflies]

pH is always lowest right before main lights come on for me. This is has to do with photosynthesis versus respiration and dissolved carbon dioxide levels (carbonic acid). Running a refugium in reverse light cycle mode can even it out some.