PH wise

Im just wondering what a normal swing in ph is in the average tank? Now that I can easily see what my PH is at any given time with the ACJR I am alarmed at how much of a swing I am getting. 7.8 in the AM and 8.3 in the evening. Is this to big of a swing?
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260g mixed reef, 105g sump, water blaster 7000 return, Bubble King SM 300 skimmer, Aqua Controller Jr, 4 radions, 3 Tunze 6055s,1 tunze 6065, 2 Vortech MP40s, Vortech MP20, Tunze ATO, GHL SA2 doser, 2 TLF reactors (1 carbon, 1 rowa).
http://www.canreef.com/vbulletin/showthread.php?t=50034 . Tank Video here
http://www.vimeo.com/2304609 and here
http://www.vimeo.com/16591694