which test to believe

[crazycat]

so i bought 6 kuhli loaches and 2 angelicus loaches yesterday (broke EVERY one of my rules--no buying from petland, no buying fish that JUST got put in the tanks--but they were REALLY nice!)

i put them in a qt tank so i can observe to make sure they're ok. one of the kuhlis died within an hour of acclimating him (which took about an hour). the rest of the fish are fine. i took the dead loach back to petland with a water sample so they could replace him. when they tested my water (with an aquarium pharmaceuticals test), the ph was really high--up around 8.0. this worried me, so i bought some peat moss. i took out the small pieces of texas holey rock. i also tested the water with my tetratest ph test. my result was 7.0--MUCH more doable than petland's test.

which test do you think i should believe?

 

[Toirtis]

Yours.....chances are the shop's reagents are old, tubes are not clean, staff are sloppy/incompetent....or some combination of the three.

 

[jsoong]

You can double check with the KH test.

There is a fixed relationship between the KH, pH & CO2.

If you let the water equilibrate to air (say sit in a cup overnight, or a few hours with an airstone) the CO2 would be atmopheric (0.03%)

Now measure the KH and PH or that water.

If the pH is 7.0, the KH should be 1.
If the pH is 8.0, the KH should be 10.

For other numbers, you can use this calculator:
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

This is a good way to double check the accuracy of your tests.

 

[Jchillin]

Cat - NYC tap water cannot get to 8 even if it wanted to...it's just not possible. I have to agree that their test is invalid. You're kh shouldn't be high either...just hoovering around the 3-4dkh mark.

 

[crazycat]

phew! thanks! guess i'll be returning that peat moss

 

[jsoong]

Another way to test your pH test is to test the pH of known samples.

pure distilled water should have pH of 7.0 (in practice it is a bit lower 6.8 ish due to CO2)

1 meq/ml solution of baking soda (NaHCO3) (85 mg per ml) should read 8.0

0.9% saline (9 grams of salt per 1000ml) should read in the 6's.

If your test is close to the theoretical number, trust yours.

Although your tap may not be 8.0 with a low KH ..... if you have rocks etc. that dissolves, the KH can rise and it is possible to have 8.0 water.

 

[Jchillin]

I agree...test your tap against your tank water.

 

[crazycat]

i removed the texas holy rock (known for bringing up ph) minutes before i tested. this wouldn't have been enough time for the ph to go down right?

 

[TomK2]

Nope, the pH would not go down until you water changed all the carbonate out.