High Ph or Low Ph?

Tommy Gun · 09-28-2006, 06:05 PM

Hello again everyone!

I was just testing my water parameters (about to do a water change and I was curious to see how bad the water might be) and realized that I can test for high range Ph and I get a reading of about 8.3 to 8.5, but I can also test in the low range and get a reading of 7.6. The color on the low range ph is not exactly the brightest blue (which would be a strong 7.6 reading), so I am not sure what test is the right one to follow!

I am also wondering if anyone knew how to do the calculations to turn my test readings from metric (usually mg/L) into american (not sure if its american or not, but ppm or parts per million). I notice that in most forums, everybody speaks in terms of ppm instead of mg/L, so I wanted to be able to understand both.

Thanks again for all your help!

Jay · 09-28-2006, 07:57 PM

Milligram Per Liter are equal to Parts Per Million. Metric/US

A lot of pH kits are separated into High and Low depending on the sensitivity of the reagents to react accurately to a High Ph 8.5 or a Low one of 6. I hate to tell you this but you need to make a field judgement of where you think the pH is or calibrate the test with a solution of a known pH where you can definitely identify the color.

Hobby test kits are a trial and ballpark at best. Use your best common sense based on your judgement of the best color match. I often get my Wife to consult.

Jay

Tommy Gun · 09-28-2006, 08:23 PM

Good point about using the wife, she is definately more attuned to the world at most times than I am!

So, my thinking was, that my Ph would be higher in a saltwater tank, than in my freshwater tank, which almost always is at or near 7.4. This is the reason why until today, i assumed I would need to use the high range Ph on my salty tank. Of course, like I said, curiosity got the best of me and I had to test using both.

So, the two questions are....Would my assumption have some truth to it in terms of saltwater versus freshwater? And, is a Ph in my salty tank of about 8.4 a good or bad thing?

ahill3780 · 09-29-2006, 11:43 AM

Hey Tommy,

You want to use the High Range pH test for your SW tank. SW Tanks should be kept between 7.8 - 8.5 and thus would never need a test kit for the Low Range. If it does then you know you have a problem and need to adjust it.

The ideal range for pH in SW is 8.3 if you go by all the printed recommendations of manufacturers. I have had my tank as low as 7.9 and as high as 8.4 and I have never had any real issues stem from this. It is never a sudden change and usually moves up/down 1 degree every few days so that is acceptable.

HTH,
Aaron

Tommy Gun · 09-29-2006, 05:17 PM

Thanks for the info guys. Knowing that I have both saltwater and freshwater tanks, I simply jumped for the 'master test kit' at the LFS, and so this is why it came with both high range and low range Ph tests. This was a lot cheaper than buying two test kits, one for each type of tank. My Ph has been holding at 8.3 to 8.5 since the begining. The color on the color chart is a shade of blue (or purple-ish) that could be close to each number, and so it would be logical to think it is somewhere in the middle of them, or 8.4.

Thanks again