What is acceptable PH Swing

[hilde123]

What is an acceptable PH swing for a SPS dominated tank? Mine goes from 7.85+/- .05 in the morning to 8.05+/- .05 in the evening. Is this stressful on corals? I am running alk @ 10 DKH and a refugium on reverse photoperiod along with air stones in sump and refugium (drawing outside air) to help blow off excess CO2.

[2thdeekay]

Your pH swing seems to be just fine. Many successful sps reefers have a wider pH swing than yours. Also, the more gradual the swing the better. I think typical pristine reefs are 8.0-8.3

[Flipper62]

A good PH reading is between 8.1 to 8.3.

Here is a Great artical from Randy Holme Farley on Parameters. IMO opinion, its a must read.

http://www.reefkeeping.com/issues/2004-05/rhf/index.php

[2thdeekay]

Recommended range from that article "7.8-8.5 is ok, where 8.1-8.3 is better"

A smaller pH swing (between 7.8-7.9 for example) would be more desirable than a larger swing between 8.1-8.3

[hilde123]

Is there any other method for reducing the swing other than the 4 items I have implemented:
1. Refugium on reverse photoperiod
2. Increased Alk - Running at 10.0
3. Strong Airation - I have 2 10 inch air stones in Refugium and sump which draw fresh air from outdoors (help blow off excess CO2)
4. Exhaust Fan for air circulation in fish room (~80 CFM) to keep fresh air in room

[Billybeau1]

While I do not see your swing as being harmful, if you want peace of mind, you could drip limewater (kalk) at night to help minimize the swing.

Personally, I would just leave it be. :)