OK I think I've got the whole ammonia, nitrite, nitrates thing figured out. Now I want to understand pH, gh and kh and how they relate to one another.

Here are my numbers:
tap pH: 7.2
gh: 151 ppm
kh: 106 ppm

(The numbers for gh and kh are averages provided to me by my city water department. How much do these numbers fluctuate and how often should I test them?)

The pH of my tank runs 7.6 range (usually between 7.4 and 7.8 but rarely that high). What makes the pH rise in the tank? If I do a 25%-50% water change, am I safe with a tap pH of 7.2 and tank pH 7.6? I'm assuming it's ok because the average would be 7.4 and I believe I've read in other posts that 0.2 change in pH is tolerable.

Thanks for the help!

Hi - Here are some articles that helped me alot!

http://thegab.org/Articles/WaterQuality.html

http://faq.thekrib.com/begin-chem.html

http://www.drhelm.com/aquarium/chemistry.html

Personally, I test regularly for these values by comparing the tap and tank valsues. I use FW Master kit for the baasic tests and I keep test strips around to double check the liquid tests and have a quick check on gH and KH. I find the test strips very hard to read (and somewhat inaccurate) for pH, so I use both tests.

When you say the tap pH is 7.2 and the tank pH is 7.4 - when are you reading the tank pH - beofre or after a water change?

Thanks for the links. I use the AP Master Test Kit for pH, ammonia, nitrites and nitrates. I'll have to pick up tests for gh and kh.

My tank pH is usually 7.6 BEFORE a water change. So it rises over a week's time (between water changes). But I guess if it starts at 7.6 and I do a 50% water change with tap water (pH 7.2) it averages to 7.4, which should be easily tolerated.

What makes it rise to 7.6 over time?

Definitely read through those articles Graham listed ...that should give you a solid understanding of the relationships of GH, KH, and pH.

Remember...a steady, consistent level is far more important than a specific number. Goldfish are very adaptable to most ranges of common water parameters.

If you have standard store bought aquarium gravel it is probably the cause of your pH rise. But in my opinion the change you are mentioning will not be harmful to the goldies at all. and neither will be doing water changes with that little of a difference in the pH.

Since there seems to be a raised interest on the board in pH, KH, and GH I would like to make some quick points. Don't get caught up in having a specific number for a water parameter. It will drive you crazy, I know it drove me crazy. Instead aim for a specific range. In addition the test kits we use are not very precise at all, especially the dip strips!! Liquid tests are a little better but still underqualified for precise readings. Ever notice how your pH test kit will read 7.6 and 7.4 but not 7.5? That is not a very precise test! The greater the difference between adjacent readings the less precise the test is.

Kevin

And here are some more interesting articles in regards that will help with understanding ph,kh and gh and how they work together.

http://www.koivetforums.com/forums/showthread.php?t=17208

http://www.koivetforums.com/forums/showthread.php?t=17677

http://www.koivetforums.com/forums/showthread.php?t=18476

http://www.koivetforums.com/forums/showthread.php?t=18476