Why does PH swing?

[JJ4417]

This might be a little light for this forum, but I can't find a good answer. Does anyone have a link, or can explain, why ph swings?

Thanks...

[bertoni]

The most common reason for pH swings in a tank is that photosynthesis consumes carbon dioxide from the water, and raises pH. This article discusses the issue:

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

[JJ4417]

Which explains why people run fuge lights opposite DT lights.

Thank you!

[bertoni]

You're welcome!