Water change...how much per week?

[t3r]

Hi guys..as most of us inject cardon dioxide into our tanks,the Ph reading of our tanks sld be ard 6 point smthing.When we change the water,does the Ph go up significantly and shock our fishes?If so...how do we minimize this kinda shock to our fishes?How much water change is too much?50%?

[juggler]

Usually I do 50% per week or fortnightly. And the pH is usually near to 7.

[vinz]

The pH scale is actually negative log. Meaning that a drop of 1 pH is 10x more acidic. E.g.
* 5 pH is 10x more acidic then 6 pH
* 6 pH is 10x more acidic then 7 pH
* 5 pH is 100x more acidic then 7 pH

If you mix equal amounts of pH 6 and pH 7 water together, the final pH is around 6.1 pH. So not much of a change if you want the water to remain low pH. However, if you are keeping fishes that prefer higher pH, it's a different story.

Btw, PUB website states that our tap water ranges from 7 to 9 pH. My home's tap water is about 8 pH.

[joe]

Anywhere from 20-50% is good for planted tanks

[CT]

I normally change around 40% - 60% of the water each water

[Aeon]

Like vinz said, the pH adjustment wouldn't be too high.
I usually change enough so I get around 5-10ppm of nitrates left for the week... around 40%-50%