Ph Drops 1+ Points After H2O Change.

[thedayawaits]

Hello all,

Two days ago I changed (50%) and gravel vacuumed my tanks and now I noticed that the pH has dropped in all of them to 6 or below from an average pH of around 7.
Why is this fluctuation and what can I do to avoid it?

The pH of tapwater which has been sitting in a jug for two days is 7.4

 

[OldMan47]

It may have something to say about the pH of tap water at its initial value and its value after a couple of days. Tap water is often manipulated by your supplier to achieve some particular value. Where I live the tap water has chloramine added to such a large extent that once I add dechlorinator, I measure over 1 ppm of ammonia in my new water. What we need to decide, as fish keepers, is what we are willing to accept in our tap water and where we need to object to the water management policies of our local suppliers. I find that I can work well within the limits that my own supplier uses so I do not object to it. I am equally certain that this would not be the case for other local interests. It may well be that we need to restrict the use of chloramines, for example.