First of all what is your pH? The reason I ask is that this is usually only a problem when it comes to dosing kalk. Although there are many recommended pH values, IMO up to 8.5 is fine, with 8.6 being an absolute limit. I shoot for 8.2 to 8.4, but it is more of the swings that should be looked after. Also, depending on the time of the day you tested, it is typical for pH in healthy tanks to swing up to .4 (8.0 to 8.4 for example). I counteract my drop through a kalk drip at night. pH will also tend to lower over time in aquariums due to a build up of acids, so water changes are key. That's a lot to take in, but usually the worry is LOW pH as opposed to high. If you use a test, test in the morning before the lights go on, and then later in the day a couple hours before the lights shut off. There will DEFINATELY be a difference, although you may not see it with a standard color tester. HTH