ORP dropping???

[Europhyllia]

pH of 7.8 has been the normal forever. It does raise very slightly with all the lights on. I have a pinpoint probe, and also test with a test kit occasionally. I used to freak out about it, but I have accepted it. I do run a calc reactor and run my lights in the sump opposite. Yesterday, with the cooler morning we had I was even able to let some fresh air in, but the highest it got was about 7.85 in the afternoon.

Here's some info from my favorite pH source ;)

That the alkalinity is at least 2.5 meq/L, and preferably higher at the lower end of this pH range. This statement is based partly on the fact that many reef aquaria operate quite effectively in the pH 7.8 to 8.0 range, but that most of the best examples of these types of tanks incorporate calcium carbonate/carbon dioxide reactors that, while tending to lower the pH, keep the carbonate alkalinity fairly high (at or above 3 meq/L.). In this case, any problems associated with calcification at these lower pH values may be offset by the higher alkalinity. Low pH primarily stresses calcifying organisms by making it harder for them to obtain sufficient carbonate to deposit skeletons. Raising the alkalinity mitigates this difficulty for reasons that are detailed later in this article.

http://www.reefkeeping.com/issues/2004-09/rhf/index.php